---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
PlanS_conform: '1'
_id: '21998'
abstract:
- lang: eng
text: Little Red Dots (LRDs), among the most enigmatic high-redshift discoveries
by JWST, are commonly believed to be powered by accreting supermassive black holes.
Here, we explore the possibility that these sources are globular clusters in formation,
with rest-frame UV arising from a very young stellar population and rest-frame
optical from a short-lived supermassive (>104 M⊙) star. The spectral profiles
of LRDs are broadly consistent with this scenario, though the observed temperatures
and bolometric luminosities favor emission reprocessed by optically thick continuum-driven
winds not fully captured by current models. The LRD z ∼ 5−7 UV luminosity function
naturally evolves, under standard evolutionary and mass-loss prescriptions, into
a present-day mass function with a turnover at log10(M*/M⊙) = 5.3 and an exponential
cutoff at high masses, consistent with local globular cluster populations. We
estimate the total present-day number density of LRDs formed across all redshifts
to be ≈0.3 Mpc−3, similar within uncertainties to local globular clusters. The
observed LRD redshift range matches the age distribution of metal-poor globular
clusters, without current LRD counterparts to the metal-rich population. If LRDs
are globular clusters in formation, we predict chemical abundance patterns characteristic
of multiple stellar populations, including enhanced He and N, and potential Na–O
and Al–Mg anticorrelations. These results offer a local perspective to explore
this surprisingly abundant population of distant sources, and a potential new
window into extreme stellar astrophysics in the early Universe.
acknowledgement: "We thank the referees for detailed and highly constructive reports
that significantly improved the scope and breadth of the manuscript. J.C. thanks
Hollis Akins, Volker Bromm, Rui Chaves-Marques, Steve Finkelstein, Karl Gebhardt,
Keith Hawkins, Harley Katz, Stellar Offner, Daniel Schaerer, Grace Telford, and
Jorick Vink for conversations that improved the Letter. A.d.G. acknowledges support
from a Clay Fellowship awarded by the Smithsonian Astrophysical Observatory. M.B.K.
acknowledges support from NSF grants AST-2108962 and AST-2408247; NASA grant 80NSSC22K0827;
HST-GO-16686, HST-AR-17028, JWST-GO-03788, and JWST-AR-06278 from the Space Telescope
Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555;
and from the Samuel T. and Fern Yanagisawa Regents Professorship in Astronomy at
UT Austin. A.A.C.S. acknowledges support by the Deutsche Forschungsgemeinschaft
(DFG, German Research Foundation) in the form of an Emmy Noether Research Group—Project-ID
445674056 (SA4064/1-1, PI Sander). A.A.C.S. further acknowledges support from the
Deutsches Zentrum für Luft und Raumfahrt (DLR) grant grants 50 OR 2509 (PI: A.A.C.
Sander) and 50 OR 2306 (PI: V. Ramachandran/A.A.C. Sander) as well as from the Federal
Ministry of Research, Technology, and Space (BMFTR) and the Baden-Württemberg Ministry
of Science as part of the Excellence Strategy of the German Federal and State Governments.
This project was cofunded by the European Union (Project 101183150—OCEANS).\r\n\r\nThis
work is based in part on observations made with the NASA/ESA/CSA James Webb Space
Telescope. The data were obtained from the Mikulski Archive for Space Telescopes
at the Space Telescope Science Institute, which is operated by the Association of
Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for
JWST. These observations are associated with programs 1180, 1181, 1208, 1212, 1213,
1215, 1286, 1345, 1433, 2198, 2561, 2750, 2767, 4106, 4233, 5105, 5224, 6368, and
6585."
article_number: L4
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: John
full_name: Chisholm, John
last_name: Chisholm
- first_name: Danielle A.
full_name: Berg, Danielle A.
last_name: Berg
- first_name: Michael
full_name: Boylan-Kolchin, Michael
last_name: Boylan-Kolchin
- first_name: Anna
full_name: De Graaff, Anna
last_name: De Graaff
- first_name: Lukas J.
full_name: Furtak, Lukas J.
last_name: Furtak
- first_name: Vasily
full_name: Kokorev, Vasily
last_name: Kokorev
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Julian B.
full_name: Muñoz, Julian B.
last_name: Muñoz
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: Andreas A.C.
full_name: Sander, Andreas A.C.
last_name: Sander
citation:
ama: Chisholm J, Berg DA, Boylan-Kolchin M, et al. Little Red Dots as globular clusters
in formation. The Astrophysical Journal Letters. 2026;1004(1). doi:10.3847/2041-8213/ae6dae
apa: Chisholm, J., Berg, D. A., Boylan-Kolchin, M., De Graaff, A., Furtak, L. J.,
Kokorev, V., … Sander, A. A. C. (2026). Little Red Dots as globular clusters in
formation. The Astrophysical Journal Letters. IOP Publishing. https://doi.org/10.3847/2041-8213/ae6dae
chicago: Chisholm, John, Danielle A. Berg, Michael Boylan-Kolchin, Anna De Graaff,
Lukas J. Furtak, Vasily Kokorev, Jorryt J Matthee, Julian B. Muñoz, Rohan P. Naidu,
and Andreas A.C. Sander. “Little Red Dots as Globular Clusters in Formation.”
The Astrophysical Journal Letters. IOP Publishing, 2026. https://doi.org/10.3847/2041-8213/ae6dae.
ieee: J. Chisholm et al., “Little Red Dots as globular clusters in formation,”
The Astrophysical Journal Letters, vol. 1004, no. 1. IOP Publishing, 2026.
ista: Chisholm J, Berg DA, Boylan-Kolchin M, De Graaff A, Furtak LJ, Kokorev V,
Matthee JJ, Muñoz JB, Naidu RP, Sander AAC. 2026. Little Red Dots as globular
clusters in formation. The Astrophysical Journal Letters. 1004(1), L4.
mla: Chisholm, John, et al. “Little Red Dots as Globular Clusters in Formation.”
The Astrophysical Journal Letters, vol. 1004, no. 1, L4, IOP Publishing,
2026, doi:10.3847/2041-8213/ae6dae.
short: J. Chisholm, D.A. Berg, M. Boylan-Kolchin, A. De Graaff, L.J. Furtak, V.
Kokorev, J.J. Matthee, J.B. Muñoz, R.P. Naidu, A.A.C. Sander, The Astrophysical
Journal Letters 1004 (2026).
date_created: 2026-06-14T22:01:42Z
date_published: 2026-06-10T00:00:00Z
date_updated: 2026-06-19T09:50:33Z
day: '10'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.3847/2041-8213/ae6dae
external_id:
arxiv:
- '2602.15935'
file:
- access_level: open_access
checksum: 66949af6e620c8ef37de42688829a3e3
content_type: application/pdf
creator: dernst
date_created: 2026-06-19T09:45:21Z
date_updated: 2026-06-19T09:45:21Z
file_id: '22098'
file_name: 2026_AstrophysicalJourLetters_Chisholm.pdf
file_size: 919919
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success: 1
file_date_updated: 2026-06-19T09:45:21Z
has_accepted_license: '1'
intvolume: ' 1004'
issue: '1'
language:
- iso: eng
month: '06'
oa: 1
oa_version: Published Version
publication: The Astrophysical Journal Letters
publication_identifier:
eissn:
- 2041-8213
issn:
- 2041-8205
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
scopus_import: '1'
status: public
title: Little Red Dots as globular clusters in formation
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 1004
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
PlanS_conform: '1'
_id: '21999'
abstract:
- lang: eng
text: JWST has revealed an abundance of supermassive black holes (BHs) in the early
Universe, and yet the lowest mass seed BHs that gave rise to these populations
remain elusive. Here, we present a systematic search for broad-line active galactic
nuclei (AGNs) in some of the faintest high-z galaxies surveyed yet by combining
ultra-deep JWST/NIRSpec G395M spectroscopy with the strong lensing aid in AS1063.
By employing the profile of the [O iii]λ5007 emission lines as a template for
narrow-line components and carefully cross-validating with mock observations,
we identify a sample of 10 broad-line AGNs at 4.5 < z < 7.0 (eight secure, two
tentative). The inferred BH masses from the broad Hα line explore the intermediate
BH mass regime down to ∼105.5 M⊙. The stellar mass (M*) is estimated with a galaxy+AGN
composite model, and we find the BH to stellar mass ratio spans down to MBH/M*
≲ 0.1%, unveiling populations on the empirical MBH–M* relation observed in the
local Universe. We also derive the BH mass function and investigate its low-mass
end at this epoch. While we confirm the agreement of our results with previous
studies at MBH ≳ 106.5M⊙, we find the mass range of ∼105.5 M⊙ features an enhanced
abundance with respect to the extrapolated best-fit Schechter function. Comparison
with theoretical models suggests that a possible origin for this enhanced abundance
is the direct-collapse BH formation, supporting the scenario that the direct collapse
of massive gas clouds is a significant pathway for the earliest supermassive BHs.
acknowledgement: 'We thank the anonymous referee for insightful comments, which significantly
improved the manuscript. We acknowledge Kohei Inayoshi for helpful discussions.
This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope.
The data were obtained from the Mikulski Archive for Space Telescopes at the Space
Telescope Science Institute, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. The specific
observations analyzed can be accessed via DOI: 10.17909/4byn-fe55 and 10.17909/v2y7-j922.
These observations are associated with programs #3293 and #9223. S.F. and Q.F. acknowledge
support from the Dunlap Institute, which is funded through an endowment established
by the David Dunlap family and the University of Toronto. A.S.L. acknowledges support
from the Knut and Alice Wallenberg Foundation. A.Z. acknowledges support by grant
No. 2020750 from the United States-Israel Binational Science Foundation (BSF) and
grant No. 2109066 from the United States National Science Foundation (NSF); and
by the Israel Science Foundation grant No. 864/23.'
article_number: '244'
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Qinyue
full_name: Fei, Qinyue
last_name: Fei
- first_name: Seiji
full_name: Fujimoto, Seiji
last_name: Fujimoto
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: John
full_name: Chisholm, John
last_name: Chisholm
- first_name: Hakim
full_name: Atek, Hakim
last_name: Atek
- first_name: Gabriel
full_name: Brammer, Gabriel
last_name: Brammer
- first_name: Yoshihisa
full_name: Asada, Yoshihisa
last_name: Asada
- first_name: Danielle A.
full_name: Berg, Danielle A.
last_name: Berg
- first_name: Volker
full_name: Bromm, Volker
last_name: Bromm
- first_name: Lukas J.
full_name: Furtak, Lukas J.
last_name: Furtak
- first_name: Jenny E.
full_name: Greene, Jenny E.
last_name: Greene
- first_name: Tiger Yu Yang
full_name: Hsiao, Tiger Yu Yang
last_name: Hsiao
- first_name: Junehyoung
full_name: Jeon, Junehyoung
last_name: Jeon
- first_name: Vasily
full_name: Kokorev, Vasily
last_name: Kokorev
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Priyamvada
full_name: Natarajan, Priyamvada
last_name: Natarajan
- first_name: Richard
full_name: Pan, Richard
last_name: Pan
- first_name: Johan
full_name: Richard, Johan
last_name: Richard
- first_name: Alberto
full_name: Saldana-Lopez, Alberto
last_name: Saldana-Lopez
- first_name: Daniel
full_name: Schaerer, Daniel
last_name: Schaerer
- first_name: Marta
full_name: Volonteri, Marta
last_name: Volonteri
- first_name: Adi
full_name: Zitrin, Adi
last_name: Zitrin
citation:
ama: 'Fei Q, Fujimoto S, Naidu RP, et al. A GLIMPSE of intermediate mass Black Holes
in the epoch of reionization: Witnessing the descendants of direct collapse? The
Astrophysical Journal. 2026;1003(2). doi:10.3847/1538-4357/ae6248'
apa: 'Fei, Q., Fujimoto, S., Naidu, R. P., Chisholm, J., Atek, H., Brammer, G.,
… Zitrin, A. (2026). A GLIMPSE of intermediate mass Black Holes in the epoch of
reionization: Witnessing the descendants of direct collapse? The Astrophysical
Journal. IOP Publishing. https://doi.org/10.3847/1538-4357/ae6248'
chicago: 'Fei, Qinyue, Seiji Fujimoto, Rohan P. Naidu, John Chisholm, Hakim Atek,
Gabriel Brammer, Yoshihisa Asada, et al. “A GLIMPSE of Intermediate Mass Black
Holes in the Epoch of Reionization: Witnessing the Descendants of Direct Collapse?”
The Astrophysical Journal. IOP Publishing, 2026. https://doi.org/10.3847/1538-4357/ae6248.'
ieee: 'Q. Fei et al., “A GLIMPSE of intermediate mass Black Holes in the
epoch of reionization: Witnessing the descendants of direct collapse?,” The
Astrophysical Journal, vol. 1003, no. 2. IOP Publishing, 2026.'
ista: 'Fei Q, Fujimoto S, Naidu RP, Chisholm J, Atek H, Brammer G, Asada Y, Berg
DA, Bromm V, Furtak LJ, Greene JE, Hsiao TYY, Jeon J, Kokorev V, Matthee JJ, Natarajan
P, Pan R, Richard J, Saldana-Lopez A, Schaerer D, Volonteri M, Zitrin A. 2026.
A GLIMPSE of intermediate mass Black Holes in the epoch of reionization: Witnessing
the descendants of direct collapse? The Astrophysical Journal. 1003(2), 244.'
mla: 'Fei, Qinyue, et al. “A GLIMPSE of Intermediate Mass Black Holes in the Epoch
of Reionization: Witnessing the Descendants of Direct Collapse?” The Astrophysical
Journal, vol. 1003, no. 2, 244, IOP Publishing, 2026, doi:10.3847/1538-4357/ae6248.'
short: Q. Fei, S. Fujimoto, R.P. Naidu, J. Chisholm, H. Atek, G. Brammer, Y. Asada,
D.A. Berg, V. Bromm, L.J. Furtak, J.E. Greene, T.Y.Y. Hsiao, J. Jeon, V. Kokorev,
J.J. Matthee, P. Natarajan, R. Pan, J. Richard, A. Saldana-Lopez, D. Schaerer,
M. Volonteri, A. Zitrin, The Astrophysical Journal 1003 (2026).
das_tickbox: '0'
dataavailabilitystatement: '10.17909/4byn-fe55 and 10.17909/v2y7-j922 used with Software:
LMFIT (M. Newville et al. 2014) msafit (A. de Graaff et al. 2024). - Text extracted
from Acknowledgements, no separate DAS'
date_created: 2026-06-14T22:01:43Z
date_published: 2026-06-01T00:00:00Z
date_updated: 2026-06-22T11:34:52Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.3847/1538-4357/ae6248
external_id:
arxiv:
- '2509.20452'
file:
- access_level: open_access
checksum: b04247996b8dcd0eb5387581706d1106
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creator: dernst
date_created: 2026-06-22T08:03:55Z
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file_name: 2026_AstrophysicalJour_Fei.pdf
file_size: 19681834
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has_accepted_license: '1'
intvolume: ' 1003'
issue: '2'
language:
- iso: eng
month: '06'
oa: 1
oa_version: Published Version
publication: The Astrophysical Journal
publication_identifier:
eissn:
- 1538-4357
issn:
- 0004-637X
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
researchdata_availability: yes
scopus_import: '1'
status: public
supplementarymaterial: yes
title: 'A GLIMPSE of intermediate mass Black Holes in the epoch of reionization: Witnessing
the descendants of direct collapse?'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 1003
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
PlanS_conform: '1'
_id: '21038'
abstract:
- lang: eng
text: "Little Red Dots (LRDs) are compact sources at z > 5 discovered through James
Webb Space Telescope spectroscopy. Their spectra exhibit broad Balmer emission
lines (>~1000 km s^−1), alongside absorption features and a pronounced Balmer
break – evidence for a dense, neutral hydrogen medium, in which the n = 2 state
is significantly populated. When interpreted as arising\r\nfrom active galactic
nucleus broad-line regions, inferred black hole masses from local scaling relations
exceed expectations given their stellar masses, challenging models of early black
hole–galaxy co-evolution. However, radiative transfer effects in dense media may
also impact the formation of hydrogen emission lines. We model three scattering
processes shaping hydrogen\r\nline profiles: resonance scattering by hydrogen
in the n = 2 state, Raman scattering of ultraviolet (UV) radiation by ground-state
hydrogen, and Thomson scattering by free electrons. Using 3D Monte Carlo radiative
transfer simulations, we examine their imprint on line shapes and ratios. Resonance
scattering produces strong deviations from Case B flux ratios, clear differences\r\nbetween
Hα and Hβ, and encodes gas kinematics in line profiles but cannot broaden Hβ due
to conversion to Paα. While Raman scattering can yield broad wings, scattering
of the UV continuum is disfavoured given the absence of strong full width at half-maximum
variations across transitions. Raman scattering of higher Lyman-series emission
can produce Hα/Hβ wing\r\nwidth ratios of >~1.28, agreeing with observations.
Thomson scattering can reproduce the observed >~ 1000 km s^−1 wings under plausible
conditions – e.g. Te ∼ 10^4 K and Ne ∼ 10^24 cm^−2 – and lead to black hole mass
overestimates by factors 10. Our results provide a framework for interpreting
hydrogen lines in LRDs and similar systems."
acknowledgement: "The authorsthank the anonymousreferee for constructive comments,
which improved the clarity of this paper. SJC acknowledges support from the ERC
synergy grant 101166930 – RECAP. MG thanks the Max Planck Society for support through
the Max Planck Research Group, and the European Union forsupport through ERC-2024-STG
101165038 (ReMMU). JM acknowledges funding by the European Union (ERC, AGENTS, 101076224).
CAM acknowledges support\r\nby the European Union ERC grant RISES (101163035), Carlsberg
Foundation (CF22-1322), and VILLUM FONDEN (37459). Computations were performed on
HPC systems Freya and Orion at the Max Planck Computing and Data Facility."
article_number: staf2131
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Seok Jun
full_name: Chang, Seok Jun
last_name: Chang
- first_name: Max
full_name: Gronke, Max
last_name: Gronke
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Charlotte
full_name: Mason, Charlotte
last_name: Mason
citation:
ama: Chang SJ, Gronke M, Matthee JJ, Mason C. Impact of resonance, Raman, and Thomson
scattering on hydrogen line formation in Little Red Dots. Monthly Notices of
the Royal Astronomical Society. 2026;545(4). doi:10.1093/mnras/staf2131
apa: Chang, S. J., Gronke, M., Matthee, J. J., & Mason, C. (2026). Impact of
resonance, Raman, and Thomson scattering on hydrogen line formation in Little
Red Dots. Monthly Notices of the Royal Astronomical Society. Oxford University
Press. https://doi.org/10.1093/mnras/staf2131
chicago: Chang, Seok Jun, Max Gronke, Jorryt J Matthee, and Charlotte Mason. “Impact
of Resonance, Raman, and Thomson Scattering on Hydrogen Line Formation in Little
Red Dots.” Monthly Notices of the Royal Astronomical Society. Oxford University
Press, 2026. https://doi.org/10.1093/mnras/staf2131.
ieee: S. J. Chang, M. Gronke, J. J. Matthee, and C. Mason, “Impact of resonance,
Raman, and Thomson scattering on hydrogen line formation in Little Red Dots,”
Monthly Notices of the Royal Astronomical Society, vol. 545, no. 4. Oxford
University Press, 2026.
ista: Chang SJ, Gronke M, Matthee JJ, Mason C. 2026. Impact of resonance, Raman,
and Thomson scattering on hydrogen line formation in Little Red Dots. Monthly
Notices of the Royal Astronomical Society. 545(4), staf2131.
mla: Chang, Seok Jun, et al. “Impact of Resonance, Raman, and Thomson Scattering
on Hydrogen Line Formation in Little Red Dots.” Monthly Notices of the Royal
Astronomical Society, vol. 545, no. 4, staf2131, Oxford University Press,
2026, doi:10.1093/mnras/staf2131.
short: S.J. Chang, M. Gronke, J.J. Matthee, C. Mason, Monthly Notices of the Royal
Astronomical Society 545 (2026).
date_created: 2026-01-25T23:01:39Z
date_published: 2026-02-01T00:00:00Z
date_updated: 2026-02-12T12:56:33Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1093/mnras/staf2131
external_id:
arxiv:
- '2508.08768'
file:
- access_level: open_access
checksum: 52ba7d7b5b80af0c50f57e4c2acc3930
content_type: application/pdf
creator: dernst
date_created: 2026-02-12T12:44:33Z
date_updated: 2026-02-12T12:44:33Z
file_id: '21220'
file_name: 2026_MonthNoticesRAS_Chang.pdf
file_size: 5600366
relation: main_file
success: 1
file_date_updated: 2026-02-12T12:44:33Z
has_accepted_license: '1'
intvolume: ' 545'
issue: '4'
language:
- iso: eng
month: '02'
oa: 1
oa_version: Published Version
project:
- _id: bd9b2118-d553-11ed-ba76-db24564edfea
grant_number: '101076224'
name: Young galaxies as tracers and agents of cosmic reionization
publication: Monthly Notices of the Royal Astronomical Society
publication_identifier:
eissn:
- 1365-2966
issn:
- 0035-8711
publication_status: published
publisher: Oxford University Press
quality_controlled: '1'
scopus_import: '1'
status: public
title: Impact of resonance, Raman, and Thomson scattering on hydrogen line formation
in Little Red Dots
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 545
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: diamond
PlanS_conform: '1'
_id: '21341'
abstract:
- lang: eng
text: We aim to characterise the mass-metallicity relation (MZR) and the 3D correlation
between the stellar mass, metallicity, and star formation rate (SFR) known as
the fundamental metallicity relation (FMR) for galaxies at 5 < z < 7. Using ∼800
[O III] selected galaxies from deep NIRCam grism surveys, we present our stacked
measurements of direct-Te metallicities, which we used to test recent strong-line
metallicity calibrations. Our measured direct-Te metallicities (0.1–0.2 Z⊙ for
M★ ≈ 5 × 107 − 9 M⊙, respectively) match recent JWST/NIRSpec-based results. However,
there are significant inconsistencies between observations and hydrodynamical
simulations. We observe a flatter MZR slope than the SPHINX20 and FLARES simulations,
which cannot be attributed to selection effects. With simple models, we show that
the effect of an [O III] flux-limited sample on the observed shape of the MZR
is strongly dependent on the FMR. If the FMR is similar to the one in the local
Universe, the intrinsic high-redshift MZR should be even flatter than is observed.
In turn, a 3D relation where SFR correlates positively with metallicity at fixed
mass would imply an intrinsically steeper MZR. Our measurements indicate that
metallicity variations at fixed mass show little dependence on the SFR, suggesting
a flat intrinsic MZR. This could indicate that the low-mass galaxies at these
redshifts are out of equilibrium and that metal enrichment occurs rapidly in low-mass
galaxies. However, being limited by our stacking analysis, we are yet to probe
the scatter in the MZR and its dependence on SFR. Large carefully selected samples
of galaxies with robust metallicity measurements can put tight constraints on
the high-redshift FMR and help us to understand the interplay between gas flows,
star formation, and feedback in early galaxies.
acknowledgement: 'We thank the anonymous referee for the insightful comments that
helped improving this paper. This work is based on observations made with the NASA/ESA/CSA
James Webb Space Telescope. The data were obtained from the Mikulski Archive for
Space Telescopes at the Space Telescope Science Institute, which is operated by
the Associations of Universities for Research in Astronomy, Inc., under NASA contract
NAS 5-03127 for JWST. These observations were taken under programmes # 1243, # 1933
and # 3516. Funded by the European Union (ERC, AGENTS, 101076224). Views and opinions
expressed are however those of the author(s) only and do not necessarily reflect
those of the European Union or the European Research Council. Neither the European
Union nor the granting authority can be held responsible for them. GK acknowledges
support from the Foundation MERAC. APV acknowledge support from the Sussex Astronomy
Centre STFC Consolidated Grant (ST/X001040/1).'
article_number: A165
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Gauri
full_name: Kotiwale, Gauri
id: 1438afc8-1ff6-11ee-9fa6-cd4a75d66875
last_name: Kotiwale
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Daichi
full_name: Kashino, Daichi
last_name: Kashino
- first_name: Aswin P.
full_name: Vijayan, Aswin P.
last_name: Vijayan
- first_name: Alberto
full_name: Torralba Torregrosa, Alberto
id: 018f0249-0e87-11f0-b167-cbce08fbd541
last_name: Torralba Torregrosa
orcid: 0000-0001-5586-6950
- first_name: Claudia
full_name: Di Cesare, Claudia
id: 2d002343-372f-11ef-98ec-a164d20427cb
last_name: Di Cesare
- first_name: Edoardo
full_name: Iani, Edoardo
id: 4053390a-6b68-11ef-9828-a3b8adef8d0a
last_name: Iani
orcid: 0000-0001-8386-3546
- first_name: Rongmon
full_name: Bordoloi, Rongmon
last_name: Bordoloi
- first_name: Joel
full_name: Leja, Joel
last_name: Leja
- first_name: Michael V.
full_name: Maseda, Michael V.
last_name: Maseda
- first_name: Sandro
full_name: Tacchella, Sandro
last_name: Tacchella
- first_name: Irene
full_name: Shivaei, Irene
last_name: Shivaei
- first_name: Kasper E.
full_name: Heintz, Kasper E.
last_name: Heintz
- first_name: A. Lola
full_name: Danhaive, A. Lola
last_name: Danhaive
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: Ivan
full_name: Kramarenko, Ivan
id: 9a9394cb-3200-11ee-973b-f5ba2a8b16e4
last_name: Kramarenko
orcid: 0000-0001-5346-6048
- first_name: Benjamín
full_name: Navarrete, Benjamín
id: aa14a535-50c9-11ef-b52e-e0c373d10148
last_name: Navarrete
- first_name: Ruari
full_name: Mackenzie, Ruari
last_name: Mackenzie
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: David
full_name: Sobral, David
last_name: Sobral
citation:
ama: Kotiwale G, Matthee JJ, Kashino D, et al. Rapid, out-of-equilibrium metal enrichment
indicated by a flat mass-metallicity relation at z ∼ 6 from NIRCam grism spectroscopy.
Astronomy & Astrophysics. 2026;706. doi:10.1051/0004-6361/202556597
apa: Kotiwale, G., Matthee, J. J., Kashino, D., Vijayan, A. P., Torralba Torregrosa,
A., Di Cesare, C., … Sobral, D. (2026). Rapid, out-of-equilibrium metal enrichment
indicated by a flat mass-metallicity relation at z ∼ 6 from NIRCam grism spectroscopy.
Astronomy & Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/202556597
chicago: Kotiwale, Gauri, Jorryt J Matthee, Daichi Kashino, Aswin P. Vijayan, Alberto
Torralba Torregrosa, Claudia Di Cesare, Edoardo Iani, et al. “Rapid, out-of-Equilibrium
Metal Enrichment Indicated by a Flat Mass-Metallicity Relation at z ∼ 6 from NIRCam
Grism Spectroscopy.” Astronomy & Astrophysics. EDP Sciences, 2026.
https://doi.org/10.1051/0004-6361/202556597.
ieee: G. Kotiwale et al., “Rapid, out-of-equilibrium metal enrichment indicated
by a flat mass-metallicity relation at z ∼ 6 from NIRCam grism spectroscopy,”
Astronomy & Astrophysics, vol. 706. EDP Sciences, 2026.
ista: Kotiwale G, Matthee JJ, Kashino D, Vijayan AP, Torralba Torregrosa A, Di Cesare
C, Iani E, Bordoloi R, Leja J, Maseda MV, Tacchella S, Shivaei I, Heintz KE, Danhaive
AL, Mascia S, Kramarenko I, Navarrete B, Mackenzie R, Naidu RP, Sobral D. 2026.
Rapid, out-of-equilibrium metal enrichment indicated by a flat mass-metallicity
relation at z ∼ 6 from NIRCam grism spectroscopy. Astronomy & Astrophysics.
706, A165.
mla: Kotiwale, Gauri, et al. “Rapid, out-of-Equilibrium Metal Enrichment Indicated
by a Flat Mass-Metallicity Relation at z ∼ 6 from NIRCam Grism Spectroscopy.”
Astronomy & Astrophysics, vol. 706, A165, EDP Sciences, 2026, doi:10.1051/0004-6361/202556597.
short: G. Kotiwale, J.J. Matthee, D. Kashino, A.P. Vijayan, A. Torralba Torregrosa,
C. Di Cesare, E. Iani, R. Bordoloi, J. Leja, M.V. Maseda, S. Tacchella, I. Shivaei,
K.E. Heintz, A.L. Danhaive, S. Mascia, I. Kramarenko, B. Navarrete, R. Mackenzie,
R.P. Naidu, D. Sobral, Astronomy & Astrophysics 706 (2026).
corr_author: '1'
date_created: 2026-02-22T23:01:35Z
date_published: 2026-02-01T00:00:00Z
date_updated: 2026-02-24T07:49:42Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
- _id: GradSch
doi: 10.1051/0004-6361/202556597
external_id:
arxiv:
- '2510.19959'
file:
- access_level: open_access
checksum: 6f5849d29ad43bee32f90152f6fc0294
content_type: application/pdf
creator: dernst
date_created: 2026-02-24T07:46:47Z
date_updated: 2026-02-24T07:46:47Z
file_id: '21355'
file_name: 2026_AstronomyAstrophysics_Kotiwale.pdf
file_size: 6531719
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intvolume: ' 706'
language:
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month: '02'
oa: 1
oa_version: Published Version
project:
- _id: bd9b2118-d553-11ed-ba76-db24564edfea
grant_number: '101076224'
name: Young galaxies as tracers and agents of cosmic reionization
publication: Astronomy & Astrophysics
publication_identifier:
eissn:
- 1432-0746
issn:
- 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
scopus_import: '1'
status: public
title: Rapid, out-of-equilibrium metal enrichment indicated by a flat mass-metallicity
relation at z ∼ 6 from NIRCam grism spectroscopy
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
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...
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_id: '21342'
abstract:
- lang: eng
text: "JWST has revealed a stunning population of bright galaxies at surprisingly
early epochs, z > 10,\r\nwhere few such sources were expected. Here we present
the most distant example of this class yet – MoM-z14, a luminous (MUV = −20.2)
source in the COSMOS legacy field at zspec = 14.44+0.02−0.02 that expands the
observational frontier to a mere 280 million years after the Big Bang. The redshift
is confirmed with NIRSpec/prism spectroscopy through a sharp Lyman-α break and
≈ 3σ detections of five rest-UV emission lines. The number density of bright zspec
≈ 14 − 15 sources implied by our “Mirage or Miracle” survey spanning ≈ 350 arcmin2
is > 100× larger (182+329 −105×) than pre-JWST consensus models. The high EWs
of UV lines (≈15−35˚A) signal a rising star-formation history, with a ≈10× increase
in the last 5 Myr (SFR5Myr/SFR50Myr = 9.9 +3.0 −5.8). The source is extremely
compact (circularized re = 74+15\r\n−12 pc), and yet elongated (b/a = 0.25+0.11−0.06),
suggesting an AGN is not the dominant source of UV light. The steep UV slope (β
= −2.5 +0.2 −0.2) implies negligible dust attenuation\r\nand a young stellar population.
The absence of a strong damping wing provides tentative evidence that the immediate
surroundings of MoM-z14 may be partially ionized at a redshift where virtually
every reionization model predicts a ≈ 100% neutral fraction. The nitrogen emission
and highly supersolar [N/C]> 1 hint at an abundance pattern similar to local globular
clusters that may have once hosted luminous supermassive stars. Since this abundance
pattern is also common among the most ancient stars born in the Milky Way, we
may be directly witnessing the formation of such stars in dense clusters, connecting
galaxy evolution across the entire sweep of cosmic time. "
acknowledgement: "We thank the two anonymous referees for their insightful comments
that have strengthened this work. “Mirage or Miracle” is but the latest link in
a long chain of surveys that have built COSMOS into a premier extragalactic legacy
field. We are thankful to all the teams who have contributed to this legacy, particularly
those mentioned in §3 for leading recent JWST programs whose imaging\r\nwe have
incorporated in our analysis. We are grateful to Vasily Belokurov for help in compiling
the Milky Way reference sample featured in Fig 8. We thank Danielle Berg for sharing
a highly complete, highly decimalized NUV vacuum line list. We are grateful to our
program’s NIRSpec reviewer, Dan Coe, and program coordinator, Allison Vick, for
valuable input on our MSA design. We acknowledge illuminating conversations with
Risa Wechsler and Chao-Lin Kuo about early reionization. RPN thanks Neil Pappalardo
and Jane Pappalardo for their generous support of the MIT Pappalardo Fellowships
in Physics, and for their enthusiasm and encouragement for seeking galaxies at the
highest redshifts. RPN acknowledges funding from JWST program GO5224. Support for
this work was provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51515.001-A
awarded by the Space Telescope Science Institute, which is operated by the Association
of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.
This work has received funding from the Swiss State Secretariat for Education, Research
and Innovation (SERI) under contract number MB22.00072, as well as from the Swiss
National Science Foundation (SNSF) through project grant 200020 207349. Funded by
the European Union (ERC, AGENTS, 101076224 and HEAVYMETAL, 101071865). Views and
opinions expressed are however those of the author(s) only and do not necessarily
reflect those of\r\nthe European Union or the European Research Council. Neither
the European Union nor the granting authority can be held responsible for them.
The Cosmic Dawn Center (DAWN) is funded by the Danish National Research Foundation
under grant DNRF140. This work has also been supported by JSPS KAKENHI Grant Number
23H00131. HA acknowledges support from CNES, focused on the JWST mission, and the
Programme National Cosmology and Galaxies (PNCG)\r\nof CNRS/INSU with INP and IN2P3,
co-funded by CEA and CNES. HA is supported by the French National Research Agency
(ANR) under the project FIRSTGAL, grant number ANR-24-CE31-0838. SB is supported
by the UK Research and Innovation (UKRI) Future Leaders Fellowship [grant number
MR/V023381/1]. R.D. acknowledges support from the INAF GO 2022\r\ngrant “The birth
of the giants: JWST sheds light on the build-up of quasars at cosmic dawn” and by
the PRIN MUR “2022935STW”, RFF M4.C2.1.1, CUP J53D23001570006 and C53D23000950006.
Computations supporting this paper were run on MIT’s Engaging cluster. This publication
made use of the NASA Astrophysical Data System for bibliographic information. Some
of the data products presented herein were retrieved from the Dawn JWST Archive
(DJA). DJA is an initiative of the Cosmic Dawn Center (DAWN), which is funded by
the Danish National Research Foundation under grant DNRF140. Software used in developing
this work includes: matplotlib (Hunter 2007), jupyter (Kluyver et al. 2016), IPython
(P´erez & Granger 2007), numpy (Oliphant 2015), scipy (Virtanen et al. 2020), TOPCAT
(Taylor 2005), and Astropy (Astropy Collaboration et al. 2013).This work is based
on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data
were obtained from the Mikulski Archive for Space\r\nTelescopes at the Space Telescope
Science Institute, which is operated by the Association of Universities for Research
in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations
are associated with program # 5224."
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: Pascal A.
full_name: Oesch, Pascal A.
last_name: Oesch
- first_name: Gabriel
full_name: Brammer, Gabriel
last_name: Brammer
- first_name: Andrea
full_name: Weibel, Andrea
last_name: Weibel
- first_name: Yijia
full_name: Li, Yijia
last_name: Li
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: John
full_name: Chisholm, John
last_name: Chisholm
- first_name: Clara L.
full_name: Pollock, Clara L.
last_name: Pollock
- first_name: Kasper E.
full_name: Heintz, Kasper E.
last_name: Heintz
- first_name: Benjamin D.
full_name: Johnson, Benjamin D.
last_name: Johnson
- first_name: Xuejian
full_name: Shen, Xuejian
last_name: Shen
- first_name: Raphael E.
full_name: Hviding, Raphael E.
last_name: Hviding
- first_name: Joel
full_name: Leja, Joel
last_name: Leja
- first_name: Sandro
full_name: Tacchella, Sandro
last_name: Tacchella
- first_name: Arpita
full_name: Ganguly, Arpita
last_name: Ganguly
- first_name: Callum
full_name: Witten, Callum
last_name: Witten
- first_name: Hakim
full_name: Atek, Hakim
last_name: Atek
- first_name: Sirio
full_name: Belli, Sirio
last_name: Belli
- first_name: Sownak
full_name: Bose, Sownak
last_name: Bose
- first_name: Rychard
full_name: Bouwens, Rychard
last_name: Bouwens
- first_name: Pratika
full_name: Dayal, Pratika
last_name: Dayal
- first_name: Roberto
full_name: Decarli, Roberto
last_name: Decarli
- first_name: Anna
full_name: De Graaff, Anna
last_name: De Graaff
- first_name: Yoshinobu
full_name: Fudamoto, Yoshinobu
last_name: Fudamoto
- first_name: Emma
full_name: Giovinazzo, Emma
last_name: Giovinazzo
- first_name: Jenny E.
full_name: Greene, Jenny E.
last_name: Greene
- first_name: Garth
full_name: Illingworth, Garth
last_name: Illingworth
- first_name: Akio K.
full_name: Inoue, Akio K.
last_name: Inoue
- first_name: Sarah G.
full_name: Kane, Sarah G.
last_name: Kane
- first_name: Ivo
full_name: Labbe, Ivo
last_name: Labbe
- first_name: Ecaterina
full_name: Leonova, Ecaterina
last_name: Leonova
- first_name: Rui
full_name: Marques-Chaves, Rui
last_name: Marques-Chaves
- first_name: Romain A.
full_name: Meyer, Romain A.
last_name: Meyer
- first_name: Erica J.
full_name: Nelson, Erica J.
last_name: Nelson
- first_name: Guido
full_name: Roberts-Borsani, Guido
last_name: Roberts-Borsani
- first_name: Daniel
full_name: Schaerer, Daniel
last_name: Schaerer
- first_name: Robert A.
full_name: Simcoe, Robert A.
last_name: Simcoe
- first_name: Mauro
full_name: Stefanon, Mauro
last_name: Stefanon
- first_name: Yuma
full_name: Sugahara, Yuma
last_name: Sugahara
- first_name: Sune
full_name: Toft, Sune
last_name: Toft
- first_name: Arjen
full_name: Van Der Wel, Arjen
last_name: Van Der Wel
- first_name: Pieter
full_name: Van Dokkum, Pieter
last_name: Van Dokkum
- first_name: Fabian
full_name: Walter, Fabian
last_name: Walter
- first_name: Darach
full_name: Watson, Darach
last_name: Watson
- first_name: John R.
full_name: Weaver, John R.
last_name: Weaver
- first_name: Katherine E.
full_name: Whitaker, Katherine E.
last_name: Whitaker
citation:
ama: 'Naidu RP, Oesch PA, Brammer G, et al. A cosmic miracle: A remarkably luminous
galaxy at zspec = 14.44 confirmed with JWST. The Open Journal of Astrophysics.
2026;9. doi:10.33232/001c.156033'
apa: 'Naidu, R. P., Oesch, P. A., Brammer, G., Weibel, A., Li, Y., Matthee, J. J.,
… Whitaker, K. E. (2026). A cosmic miracle: A remarkably luminous galaxy at zspec
= 14.44 confirmed with JWST. The Open Journal of Astrophysics. Maynooth
Academic Publishing. https://doi.org/10.33232/001c.156033'
chicago: 'Naidu, Rohan P., Pascal A. Oesch, Gabriel Brammer, Andrea Weibel, Yijia
Li, Jorryt J Matthee, John Chisholm, et al. “A Cosmic Miracle: A Remarkably Luminous
Galaxy at Zspec = 14.44 Confirmed with JWST.” The Open Journal of Astrophysics.
Maynooth Academic Publishing, 2026. https://doi.org/10.33232/001c.156033.'
ieee: 'R. P. Naidu et al., “A cosmic miracle: A remarkably luminous galaxy
at zspec = 14.44 confirmed with JWST,” The Open Journal of Astrophysics,
vol. 9. Maynooth Academic Publishing, 2026.'
ista: 'Naidu RP, Oesch PA, Brammer G, Weibel A, Li Y, Matthee JJ, Chisholm J, Pollock
CL, Heintz KE, Johnson BD, Shen X, Hviding RE, Leja J, Tacchella S, Ganguly A,
Witten C, Atek H, Belli S, Bose S, Bouwens R, Dayal P, Decarli R, De Graaff A,
Fudamoto Y, Giovinazzo E, Greene JE, Illingworth G, Inoue AK, Kane SG, Labbe I,
Leonova E, Marques-Chaves R, Meyer RA, Nelson EJ, Roberts-Borsani G, Schaerer
D, Simcoe RA, Stefanon M, Sugahara Y, Toft S, Van Der Wel A, Van Dokkum P, Walter
F, Watson D, Weaver JR, Whitaker KE. 2026. A cosmic miracle: A remarkably luminous
galaxy at zspec = 14.44 confirmed with JWST. The Open Journal of Astrophysics.
9.'
mla: 'Naidu, Rohan P., et al. “A Cosmic Miracle: A Remarkably Luminous Galaxy at
Zspec = 14.44 Confirmed with JWST.” The Open Journal of Astrophysics, vol.
9, Maynooth Academic Publishing, 2026, doi:10.33232/001c.156033.'
short: R.P. Naidu, P.A. Oesch, G. Brammer, A. Weibel, Y. Li, J.J. Matthee, J. Chisholm,
C.L. Pollock, K.E. Heintz, B.D. Johnson, X. Shen, R.E. Hviding, J. Leja, S. Tacchella,
A. Ganguly, C. Witten, H. Atek, S. Belli, S. Bose, R. Bouwens, P. Dayal, R. Decarli,
A. De Graaff, Y. Fudamoto, E. Giovinazzo, J.E. Greene, G. Illingworth, A.K. Inoue,
S.G. Kane, I. Labbe, E. Leonova, R. Marques-Chaves, R.A. Meyer, E.J. Nelson, G.
Roberts-Borsani, D. Schaerer, R.A. Simcoe, M. Stefanon, Y. Sugahara, S. Toft,
A. Van Der Wel, P. Van Dokkum, F. Walter, D. Watson, J.R. Weaver, K.E. Whitaker,
The Open Journal of Astrophysics 9 (2026).
date_created: 2026-02-22T23:01:35Z
date_published: 2026-01-30T00:00:00Z
date_updated: 2026-06-16T10:47:41Z
day: '30'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.33232/001c.156033
external_id:
arxiv:
- '2505.11263'
has_accepted_license: '1'
intvolume: ' 9'
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://doi.org/10.33232/001c.156033
month: '01'
oa: 1
oa_version: Published Version
project:
- _id: bd9b2118-d553-11ed-ba76-db24564edfea
grant_number: '101076224'
name: Young galaxies as tracers and agents of cosmic reionization
publication: The Open Journal of Astrophysics
publication_identifier:
eissn:
- 2565-6120
publication_status: published
publisher: Maynooth Academic Publishing
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'A cosmic miracle: A remarkably luminous galaxy at zspec = 14.44 confirmed
with JWST'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 9
year: '2026'
...
---
OA_type: closed access
_id: '21371'
abstract:
- lang: eng
text: There may be a newly identified early phase of supermassive black hole growth
acknowledgement: The author acknowledges the support from the European Union (European
Research Council, AGENTS, 101076224).
article_processing_charge: No
article_type: comment
author:
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
citation:
ama: Matthee JJ. Black holes disguised as little red dots. Science. 2026;391(6787):767-768.
doi:10.1126/science.adz8603
apa: Matthee, J. J. (2026). Black holes disguised as little red dots. Science.
AAAS. https://doi.org/10.1126/science.adz8603
chicago: Matthee, Jorryt J. “Black Holes Disguised as Little Red Dots.” Science.
AAAS, 2026. https://doi.org/10.1126/science.adz8603.
ieee: J. J. Matthee, “Black holes disguised as little red dots,” Science,
vol. 391, no. 6787. AAAS, pp. 767–768, 2026.
ista: Matthee JJ. 2026. Black holes disguised as little red dots. Science. 391(6787),
767–768.
mla: Matthee, Jorryt J. “Black Holes Disguised as Little Red Dots.” Science,
vol. 391, no. 6787, AAAS, 2026, pp. 767–68, doi:10.1126/science.adz8603.
short: J.J. Matthee, Science 391 (2026) 767–768.
corr_author: '1'
date_created: 2026-03-01T23:01:39Z
date_published: 2026-02-19T00:00:00Z
date_updated: 2026-03-02T09:15:45Z
day: '19'
department:
- _id: JoMa
doi: 10.1126/science.adz8603
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- '41712710'
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issue: '6787'
language:
- iso: eng
month: '02'
oa_version: None
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project:
- _id: bd9b2118-d553-11ed-ba76-db24564edfea
grant_number: '101076224'
name: Young galaxies as tracers and agents of cosmic reionization
publication: Science
publication_identifier:
eissn:
- 1095-9203
publication_status: published
publisher: AAAS
quality_controlled: '1'
scopus_import: '1'
status: public
title: Black holes disguised as little red dots
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 391
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: diamond
PlanS_conform: '1'
_id: '21451'
abstract:
- lang: eng
text: The population of the little red dots (LRDs) may represent a key phase of
supermassive black hole (SMBH) growth. A cocoon of dense excited gas is emerging
as a key component to explain the most striking properties of LRDs, such as strong
Balmer breaks and Balmer absorption, as well as the weak IR emission. To dissect
the structure of LRDs, we analyzed new deep JWST/NIRSpec PRISM and G395H spectra
of FRESCO-GN-9771, one of the most luminous known LRDs at z = 5.5. These spectra
reveal a strong Balmer break, broad Balmer lines, and very narrow [O III] emission.
We revealed a forest of optical [Fe II] lines, which we argue are emerging from
a dense (nH = 109 − 10 cm−3) warm layer with electron temperature Te ≈ 7000 K.
The broad wings of Hα and Hβ have an exponential profile due to electron scattering
in this same layer. The high Hα : Hβ : Hγ flux ratio of ≈10.4 : 1 : 0.14 is an
indicator of collisional excitation and resonant scattering dominating the Balmer
line emission. A narrow Hγ component, unseen in the other two Balmer lines due
to outshining by the broad components, could trace the ISM of a normal host galaxy
with a star formation rate of ∼5 M⊙ yr−1. The warm layer is mostly opaque to Balmer
transitions, producing a characteristic P Cygni profile in the line centers suggesting
outflowing motions. This same layer is responsible for shaping the Balmer break.
The broadband spectrum can be reasonably matched by a simple photoionized slab
model that dominates the λ > 1500 Å continuum and a low-mass (∼108 M⊙) galaxy
that could explain the narrow [O III], with only a subdominant contribution to
the UV continuum. Our findings indicate that Balmer lines are not directly tracing
the gas kinematics near the SMBH and that the BH mass scale is likely much lower
than virial indicators suggest.
acknowledgement: 'We thank the scientific referee for useful and constructive comments.
We thank Ylva Götberg and Zoltan Haiman for insightful discussions about the physics
of gaseous envelopes and accretion into black holes. Funded by the European Union
(ERC, AGENTS, 101076224). Views and opinions expressed are however those of the
author(s) only and do not necessarily reflect those of the European Union or the
European Research Council. Neither the European Union nor the granting authority
can be held responsible for them. This work is based in part on observations made
with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the
Mikulski Archive for Space Telescopes at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in Astronomy,
Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated
with program #5664. This work has received funding from the Swiss State Secretariat
for Education, Research and Innovation (SERI) under contract number MB22.00072,
as well as from the Swiss National Science Foundation (SNSF) through project grant
200020_207349.'
article_number: A75
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Alberto
full_name: Torralba Torregrosa, Alberto
id: 018f0249-0e87-11f0-b167-cbce08fbd541
last_name: Torralba Torregrosa
orcid: 0000-0001-5586-6950
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Gabriele
full_name: Pezzulli, Gabriele
last_name: Pezzulli
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: Yuzo
full_name: Ishikawa, Yuzo
last_name: Ishikawa
- first_name: Gabriel B.
full_name: Brammer, Gabriel B.
last_name: Brammer
- first_name: Seok Jun
full_name: Chang, Seok Jun
last_name: Chang
- first_name: John
full_name: Chisholm, John
last_name: Chisholm
- first_name: Anna
full_name: De Graaff, Anna
last_name: De Graaff
- first_name: Francesco
full_name: D’Eugenio, Francesco
last_name: D’Eugenio
- first_name: Claudia
full_name: Di Cesare, Claudia
id: 2d002343-372f-11ef-98ec-a164d20427cb
last_name: Di Cesare
- first_name: Anna Christina
full_name: Eilers, Anna Christina
last_name: Eilers
- first_name: Jenny E.
full_name: Greene, Jenny E.
last_name: Greene
- first_name: Max
full_name: Gronke, Max
last_name: Gronke
- first_name: Edoardo
full_name: Iani, Edoardo
id: 4053390a-6b68-11ef-9828-a3b8adef8d0a
last_name: Iani
orcid: 0000-0001-8386-3546
- first_name: Vasily
full_name: Kokorev, Vasily
last_name: Kokorev
- first_name: Gauri
full_name: Kotiwale, Gauri
id: 1438afc8-1ff6-11ee-9fa6-cd4a75d66875
last_name: Kotiwale
- first_name: Ivan
full_name: Kramarenko, Ivan
id: 9a9394cb-3200-11ee-973b-f5ba2a8b16e4
last_name: Kramarenko
orcid: 0000-0001-5346-6048
- first_name: Yilun
full_name: Ma, Yilun
last_name: Ma
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: Benjamín
full_name: Navarrete, Benjamín
id: aa14a535-50c9-11ef-b52e-e0c373d10148
last_name: Navarrete
- first_name: Erica
full_name: Nelson, Erica
last_name: Nelson
- first_name: Pascal
full_name: Oesch, Pascal
last_name: Oesch
- first_name: Robert A.
full_name: Simcoe, Robert A.
last_name: Simcoe
- first_name: Stijn
full_name: Wuyts, Stijn
last_name: Wuyts
citation:
ama: Torralba Torregrosa A, Matthee JJ, Pezzulli G, et al. The warm outer layer
of a little red dot as the source of [Fe ii] and collisional Balmer lines with
scattering wings. Astronomy & Astrophysics. 2026;707. doi:10.1051/0004-6361/202557537
apa: Torralba Torregrosa, A., Matthee, J. J., Pezzulli, G., Naidu, R. P., Ishikawa,
Y., Brammer, G. B., … Wuyts, S. (2026). The warm outer layer of a little red dot
as the source of [Fe ii] and collisional Balmer lines with scattering wings. Astronomy
& Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/202557537
chicago: Torralba Torregrosa, Alberto, Jorryt J Matthee, Gabriele Pezzulli, Rohan
P. Naidu, Yuzo Ishikawa, Gabriel B. Brammer, Seok Jun Chang, et al. “The Warm
Outer Layer of a Little Red Dot as the Source of [Fe Ii] and Collisional Balmer
Lines with Scattering Wings.” Astronomy & Astrophysics. EDP Sciences,
2026. https://doi.org/10.1051/0004-6361/202557537.
ieee: A. Torralba Torregrosa et al., “The warm outer layer of a little red
dot as the source of [Fe ii] and collisional Balmer lines with scattering wings,”
Astronomy & Astrophysics, vol. 707. EDP Sciences, 2026.
ista: Torralba Torregrosa A, Matthee JJ, Pezzulli G, Naidu RP, Ishikawa Y, Brammer
GB, Chang SJ, Chisholm J, De Graaff A, D’Eugenio F, Di Cesare C, Eilers AC, Greene
JE, Gronke M, Iani E, Kokorev V, Kotiwale G, Kramarenko I, Ma Y, Mascia S, Navarrete
B, Nelson E, Oesch P, Simcoe RA, Wuyts S. 2026. The warm outer layer of a little
red dot as the source of [Fe ii] and collisional Balmer lines with scattering
wings. Astronomy & Astrophysics. 707, A75.
mla: Torralba Torregrosa, Alberto, et al. “The Warm Outer Layer of a Little Red
Dot as the Source of [Fe Ii] and Collisional Balmer Lines with Scattering Wings.”
Astronomy & Astrophysics, vol. 707, A75, EDP Sciences, 2026, doi:10.1051/0004-6361/202557537.
short: A. Torralba Torregrosa, J.J. Matthee, G. Pezzulli, R.P. Naidu, Y. Ishikawa,
G.B. Brammer, S.J. Chang, J. Chisholm, A. De Graaff, F. D’Eugenio, C. Di Cesare,
A.C. Eilers, J.E. Greene, M. Gronke, E. Iani, V. Kokorev, G. Kotiwale, I. Kramarenko,
Y. Ma, S. Mascia, B. Navarrete, E. Nelson, P. Oesch, R.A. Simcoe, S. Wuyts, Astronomy
& Astrophysics 707 (2026).
corr_author: '1'
date_created: 2026-03-15T23:01:36Z
date_published: 2026-03-01T00:00:00Z
date_updated: 2026-03-16T10:59:16Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1051/0004-6361/202557537
external_id:
arxiv:
- '2510.00103'
file:
- access_level: open_access
checksum: fcab9cb3dcf1d68612e1fdc8191643c1
content_type: application/pdf
creator: dernst
date_created: 2026-03-16T10:57:49Z
date_updated: 2026-03-16T10:57:49Z
file_id: '21460'
file_name: 2026_AstronomyAstrophysics_Torralba2.pdf
file_size: 2510157
relation: main_file
success: 1
file_date_updated: 2026-03-16T10:57:49Z
has_accepted_license: '1'
intvolume: ' 707'
language:
- iso: eng
month: '03'
oa: 1
oa_version: Published Version
project:
- _id: bd9b2118-d553-11ed-ba76-db24564edfea
grant_number: '101076224'
name: Young galaxies as tracers and agents of cosmic reionization
publication: Astronomy & Astrophysics
publication_identifier:
eissn:
- 1432-0746
issn:
- 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
scopus_import: '1'
status: public
title: The warm outer layer of a little red dot as the source of [Fe ii] and collisional
Balmer lines with scattering wings
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 707
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: diamond
PlanS_conform: '1'
_id: '21452'
abstract:
- lang: eng
text: Galaxies exhibit a tight correlation between their star formation rate (SFR)
and stellar mass over a wide redshift range known as the star-forming main sequence
(SFMS). With JWST, the SFMS can now be investigated at high redshifts down to
masses of ∼106 M⊙, using sensitive star formation rate tracers such as the Hα
emission, which allow us to probe the variability in the star formation histories.
We present inferences of the SFMS based on 316 Hα-selected galaxies at z ∼ 4 − 5
with log(M★/M⊙) = 6.4 − 10.6. These galaxies were identified behind the Abell
2744 lensing cluster with NIRCam grism spectroscopy from the survey All the Little
Things (ALT). At face value, our data suggest a shallow slope in the SFMS (SFR ∝ M★α,
with α = 0.45). After we corrected this for the Hα-flux limited nature of our
survey using a Bayesian framework, the slope steepened to α = 0.59+0.10−0.09,
whereas current data on their own are inconclusive on the mass dependence of the
scatter. These slopes differ significantly from the slope of ∼1 that is expected
from the observed evolution of the galaxy stellar mass function and from simulations.
When we fixed the slope to α = 1, we found evidence for a decreasing intrinsic
scatter with stellar mass (from ∼0.5 dex at M★ = 108 M⊙ to 0.4 dex at M★ = 1010
M⊙). This difference might be explained by a (combination of) luminosity-dependent
SFR(Hα) calibration, a population of (mini)-quenched low-mass galaxies, or underestimated
dust attenuation in high-mass galaxies. Future deep observations with different
facilities can quantify these processes, which will enable us to achieve better
insights into the variability of the star formation histories.
acknowledgement: "We thank the anonymous referee for the insightful comments that
helped improving the manuscript. We thank Romain. A. Meyer for valuable discussion,
Pierluigi Rinaldi for his help with data handling and Luca Graziani and William
McClymont for providing the dustyGadget and\r\nTHESAN-ZOOM data, respectively. Funded
by the European Union (ERC, AGENTS, 101076224). Views and opinions expressed are
however those of the author(s) only and do not necessarily reflect those of the
European Union or the European Research Council. Neither the European Union nor
the granting authority can be held responsible for them. This work is based on observations
made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from
the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in Astronomy,
Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated
with program # 3516. We acknowledge funding from JWST program GO-3516. Software
used in developing this work includes: matplotlib (Hunter 2007), numpy (Oliphant
2007), scipy (Virtanen et al. 2020), TOPCAT (Taylor 2005), and Astropy (Astropy
Collaboration 2013)."
article_number: A129
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Claudia
full_name: Di Cesare, Claudia
id: 2d002343-372f-11ef-98ec-a164d20427cb
last_name: Di Cesare
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: Alberto
full_name: Torralba, Alberto
last_name: Torralba
- first_name: Gauri
full_name: Kotiwale, Gauri
id: 1438afc8-1ff6-11ee-9fa6-cd4a75d66875
last_name: Kotiwale
- first_name: Ivan
full_name: Kramarenko, Ivan
id: 9a9394cb-3200-11ee-973b-f5ba2a8b16e4
last_name: Kramarenko
orcid: 0000-0001-5346-6048
- first_name: Jeremy
full_name: Blaizot, Jeremy
last_name: Blaizot
- first_name: Joakim
full_name: Rosdahl, Joakim
last_name: Rosdahl
- first_name: Joel
full_name: Leja, Joel
last_name: Leja
- first_name: Edoardo
full_name: Iani, Edoardo
id: 4053390a-6b68-11ef-9828-a3b8adef8d0a
last_name: Iani
orcid: 0000-0001-8386-3546
- first_name: Angela
full_name: Adamo, Angela
last_name: Adamo
- first_name: Alba
full_name: Covelo-Paz, Alba
last_name: Covelo-Paz
- first_name: Lukas J.
full_name: Furtak, Lukas J.
last_name: Furtak
- first_name: Kasper E.
full_name: Heintz, Kasper E.
last_name: Heintz
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: Benjamín
full_name: Navarrete, Benjamín
id: aa14a535-50c9-11ef-b52e-e0c373d10148
last_name: Navarrete
- first_name: Pascal A.
full_name: Oesch, Pascal A.
last_name: Oesch
- first_name: Michael
full_name: Romano, Michael
last_name: Romano
- first_name: Irene
full_name: Shivaei, Irene
last_name: Shivaei
- first_name: Sandro
full_name: Tacchella, Sandro
last_name: Tacchella
citation:
ama: 'Di Cesare C, Matthee JJ, Naidu RP, et al. The slope and scatter of the star-forming
main sequence at z ∼ 5: Reconciling observations with simulations. Astronomy
& Astrophysics. 2026;707. doi:10.1051/0004-6361/202557790'
apa: 'Di Cesare, C., Matthee, J. J., Naidu, R. P., Torralba, A., Kotiwale, G., Kramarenko,
I., … Tacchella, S. (2026). The slope and scatter of the star-forming main sequence
at z ∼ 5: Reconciling observations with simulations. Astronomy & Astrophysics.
EDP Sciences. https://doi.org/10.1051/0004-6361/202557790'
chicago: 'Di Cesare, Claudia, Jorryt J Matthee, Rohan P. Naidu, Alberto Torralba,
Gauri Kotiwale, Ivan Kramarenko, Jeremy Blaizot, et al. “The Slope and Scatter
of the Star-Forming Main Sequence at z ∼ 5: Reconciling Observations with Simulations.”
Astronomy & Astrophysics. EDP Sciences, 2026. https://doi.org/10.1051/0004-6361/202557790.'
ieee: 'C. Di Cesare et al., “The slope and scatter of the star-forming main
sequence at z ∼ 5: Reconciling observations with simulations,” Astronomy &
Astrophysics, vol. 707. EDP Sciences, 2026.'
ista: 'Di Cesare C, Matthee JJ, Naidu RP, Torralba A, Kotiwale G, Kramarenko I,
Blaizot J, Rosdahl J, Leja J, Iani E, Adamo A, Covelo-Paz A, Furtak LJ, Heintz
KE, Mascia S, Navarrete B, Oesch PA, Romano M, Shivaei I, Tacchella S. 2026. The
slope and scatter of the star-forming main sequence at z ∼ 5: Reconciling observations
with simulations. Astronomy & Astrophysics. 707, A129.'
mla: 'Di Cesare, Claudia, et al. “The Slope and Scatter of the Star-Forming Main
Sequence at z ∼ 5: Reconciling Observations with Simulations.” Astronomy &
Astrophysics, vol. 707, A129, EDP Sciences, 2026, doi:10.1051/0004-6361/202557790.'
short: C. Di Cesare, J.J. Matthee, R.P. Naidu, A. Torralba, G. Kotiwale, I. Kramarenko,
J. Blaizot, J. Rosdahl, J. Leja, E. Iani, A. Adamo, A. Covelo-Paz, L.J. Furtak,
K.E. Heintz, S. Mascia, B. Navarrete, P.A. Oesch, M. Romano, I. Shivaei, S. Tacchella,
Astronomy & Astrophysics 707 (2026).
corr_author: '1'
date_created: 2026-03-15T23:01:36Z
date_published: 2026-03-01T00:00:00Z
date_updated: 2026-03-16T10:52:44Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
- _id: GradSch
doi: 10.1051/0004-6361/202557790
external_id:
arxiv:
- '2510.19044'
file:
- access_level: open_access
checksum: c056b00ce7324849754521fde10fb7ca
content_type: application/pdf
creator: dernst
date_created: 2026-03-16T10:48:07Z
date_updated: 2026-03-16T10:48:07Z
file_id: '21459'
file_name: 2026_AstronomyAstrophysics_DiCesare.pdf
file_size: 1821411
relation: main_file
success: 1
file_date_updated: 2026-03-16T10:48:07Z
has_accepted_license: '1'
intvolume: ' 707'
language:
- iso: eng
month: '03'
oa: 1
oa_version: Published Version
project:
- _id: bd9b2118-d553-11ed-ba76-db24564edfea
grant_number: '101076224'
name: Young galaxies as tracers and agents of cosmic reionization
publication: Astronomy & Astrophysics
publication_identifier:
eissn:
- 1432-0746
issn:
- 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'The slope and scatter of the star-forming main sequence at z ∼ 5: Reconciling
observations with simulations'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 707
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: diamond
PlanS_conform: '1'
_id: '21481'
abstract:
- lang: eng
text: 'The Hα emission line in galaxies is a powerful tracer of their recent star
formation activity. With the advent of JWST, we are now able to routinely observe
Hα in galaxies at high redshift (z ≳ 3) and thus measure their star formation
rates (SFRs). However, using classical SFR(Hα) calibrations to derive the SFRs
leads to biased results because high-redshift galaxies are commonly characterized
by low metallicities and bursty star formation histories, affecting the conversion
factor between the Hα luminosity (LHα) and the SFR. We developed a set of new
SFR(Hα) calibrations that allowed us to predict the SFRs of Hα-emitters at z ≳ 3
with very little error. We used the SPHINX cosmological simulations to select
a sample of star-forming galaxies representative of the Hα-emitter population
observed with JWST. We then derived linear corrections to the classical SFR(Hα)
calibrations that took variations in the physical properties (e.g., stellar metallicities)
among individual galaxies into account. We obtained two new SFR(Hα) calibrations
that compared to the classical calibrations reduce the root mean squared error
(RMSE) in the predicted SFRs by ΔRMSE ≈ 0.04 dex and ΔRMSE ≈ 0.06 dex, respectively.
Using the recent JWST NIRCam/grism observations of Hα-emitters at z ∼ 6, we show
that the new calibrations affect the high-redshift galaxy population statistics:
(i) the estimated cosmic SFR density decreases by ΔρSFR ≈ 12%, and (ii) the observed
slope of the star formation main sequence increases by Δ∂logSFR/∂logM★ = 0.08 ± 0.02.'
acknowledgement: "We thank the anonymous referee for the insightful comments that
helped improve the manuscript. We also thank Thibault Garel, Pascal Oesch, Irene
Shivaei, Charlotte Simmonds, Andrew Hopkins, Daniel Schaerer, and Rashmi Gottumukkala
for useful comments and productive discussions. We gratefully acknowledge support
from the CBPsmn (PSMN, Pôle Scientifique de Modélisation Numérique) of the ENS de
Lyon for the computing resources.\r\nFunded by the European Union (ERC, AGENTS,
101076224). Views and opinions expressed are however those of the author(s) only
and do not necessarily reflect those of the European Union or the European Research
Council. Neither the European Union nor the granting authority can be held responsible
for them. This work made extensive use of several open-source software packages,
and we gratefully acknowledge the efforts of their authors: numpy (Harris et al.
2020), astropy (Astropy Collaboration 2022), matplotlib (Hunter 2007), ipython (Perez
& Granger 2007), and scikit-learn (Pedregosa et al. 2011)."
article_number: A184
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Ivan
full_name: Kramarenko, Ivan
id: 9a9394cb-3200-11ee-973b-f5ba2a8b16e4
last_name: Kramarenko
orcid: 0000-0001-5346-6048
- first_name: J.
full_name: Rosdahl, J.
last_name: Rosdahl
- first_name: J.
full_name: Blaizot, J.
last_name: Blaizot
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: H.
full_name: Katz, H.
last_name: Katz
- first_name: Claudia
full_name: Di Cesare, Claudia
id: 2d002343-372f-11ef-98ec-a164d20427cb
last_name: Di Cesare
citation:
ama: Kramarenko I, Rosdahl J, Blaizot J, Matthee JJ, Katz H, Di Cesare C. H α as
a tracer of star formation in the SPHINX cosmological simulations. Astronomy
& Astrophysics. 2026;707. doi:10.1051/0004-6361/202557114
apa: Kramarenko, I., Rosdahl, J., Blaizot, J., Matthee, J. J., Katz, H., & Di
Cesare, C. (2026). H α as a tracer of star formation in the SPHINX cosmological
simulations. Astronomy & Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/202557114
chicago: Kramarenko, Ivan, J. Rosdahl, J. Blaizot, Jorryt J Matthee, H. Katz, and
Claudia Di Cesare. “H α as a Tracer of Star Formation in the SPHINX Cosmological
Simulations.” Astronomy & Astrophysics. EDP Sciences, 2026. https://doi.org/10.1051/0004-6361/202557114.
ieee: I. Kramarenko, J. Rosdahl, J. Blaizot, J. J. Matthee, H. Katz, and C. Di Cesare,
“H α as a tracer of star formation in the SPHINX cosmological simulations,” Astronomy
& Astrophysics, vol. 707. EDP Sciences, 2026.
ista: Kramarenko I, Rosdahl J, Blaizot J, Matthee JJ, Katz H, Di Cesare C. 2026.
H α as a tracer of star formation in the SPHINX cosmological simulations. Astronomy
& Astrophysics. 707, A184.
mla: Kramarenko, Ivan, et al. “H α as a Tracer of Star Formation in the SPHINX Cosmological
Simulations.” Astronomy & Astrophysics, vol. 707, A184, EDP Sciences,
2026, doi:10.1051/0004-6361/202557114.
short: I. Kramarenko, J. Rosdahl, J. Blaizot, J.J. Matthee, H. Katz, C. Di Cesare,
Astronomy & Astrophysics 707 (2026).
corr_author: '1'
date_created: 2026-03-23T14:58:03Z
date_published: 2026-03-05T00:00:00Z
date_updated: 2026-03-23T15:46:31Z
day: '05'
ddc:
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- _id: JoMa
doi: 10.1051/0004-6361/202557114
external_id:
arxiv:
- '2509.05403'
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month: '03'
oa: 1
oa_version: Published Version
project:
- _id: bd9b2118-d553-11ed-ba76-db24564edfea
grant_number: '101076224'
name: Young galaxies as tracers and agents of cosmic reionization
publication: Astronomy & Astrophysics
publication_identifier:
eissn:
- 1432-0746
issn:
- 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
status: public
title: H α as a tracer of star formation in the SPHINX cosmological simulations
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 707
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
_id: '21709'
abstract:
- lang: eng
text: 'JWST’s “little red dots” (LRDs) are increasingly interpreted as active galactic
nuclei (AGN) obscured by dense thermalized gas rather than dust as evidenced by
their X-ray weakness, blackbody-like continua, and Balmer line profiles. Key questions
are how LRDs connect to standard UV-luminous AGN, whether transitional phases
exist, and whether they are observable. We present the “X-ray dot” (XRD), a compact
source at z = 3.28 observed by the NIRSpec Wide Guaranteed Time Observation survey.
The XRD exhibits LRD hallmarks: a blackbody-like (Teff ≃ 6400 K) red continuum,
a faint but blue rest-UV excess, falling mid-IR emission, and broad Balmer lines
(FWHM ∼ 2700–3200 km s−1). Unlike LRDs, however, it is remarkably X-ray luminous
(L2−10 keV = 1044.18 erg s−1) and has a continuum inflection that is blueward
of the Balmer limit. We find that the red rest-optical and blue mid-IR continuum
cannot be reproduced by standard dust-attenuated AGN models without invoking extremely
steep extinction curves, nor can the weak mid-IR emission be reconciled with well-established
X-ray–torus scaling relations. We therefore consider an alternative scenario:
the XRD may be an LRD in transition, where the gas envelope dominates the optical
continuum but optically thin sight lines allow X-rays to escape. The XRD may thus
provide a physical link between LRDs and standard AGN, offering direct evidence
that LRDs are powered by supermassive black holes and providing insight into their
accretion properties.'
acknowledgement: "We would like to thank the anonymous reviewer for their constructive
comments, which improved the final manuscript.\r\n\r\nWe thank Bernd Husemann for
his critical contributions to the NIRSpec Wide GTO survey, and in particular his
help in selecting high-priority X-ray-luminous targets.\r\n\r\nR.E.H. acknowledges
support by the German Aerospace Center (DLR) and the Federal Ministry for Economic
Affairs and Energy (BMWi) through program 50OR2403 “RUBIES.” A.d.G. acknowledges
support from a Clay Fellowship awarded by the Smithsonian Astrophysical Observatory.
A.J.B. acknowledges funding from the “FirstGalaxies” Advanced grant from the European
Research Council (ERC) under the European Union’s Horizon 2020 research and innovation
program (grant agreement No. 789056). R.P.N. thanks Neil Pappalardo and Jane Pappalardo
for their generous support of the MIT Pappalardo Fellowships in Physics. Support
for this work was provided by the Brinson Foundation through a Brinson Prize Fellowship
grant. H.Ü. acknowledges funding by the European Union (ERC APEX, 101164796). Views
and opinions expressed are, however, those of the authors only and do not necessarily
reflect those of the European Union or the European Research Council Executive Agency.
Neither the European Union nor the granting authority can be held responsible for
them. G.V. acknowledges support from European Union’s HE ERC Starting grant No.
101040227—WINGS. B.W. acknowledges support provided by NASA through Hubble Fellowship
grant HST-HF2-51592.001 awarded by the Space Telescope Science Institute, which
is operated by the Association of Universities for Research in Astronomy, In., for
NASA, under the contract NAS 5-26555.\r\n\r\nThe data products presented herein
were retrieved from the Dawn JWST Archive (DJA). DJA is an initiative of the Cosmic
Dawn Center (DAWN).\r\n\r\nThis work is based in part on observations made with
the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski
Archive for Space Telescopes at the Space Telescope Science Institute, which is
operated by the Association of Universities for Research in Astronomy, Inc., under
NASA contract NAS 5-03127 for JWST. These observations are associated with programs
Nos. GTO-1213. The data described here may be obtained from the MAST archive at
DOI: 10.17909/qffz-b324.\r\n\r\nThis Letter employs a list of Chandra datasets,
obtained by the Chandra X-ray Observatory, contained in DOI: 10.25574/cdc.540.\r\n\r\nThis
work is based on observations taken by the 3D-HST Treasury Program (GO 12177 and
12328) with the NASA/ESA HST, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS5-26555.\r\n\r\nThis work
makes use of color palettes created by Martin Krzywinski designed for colorblindness.
The color palettes and more information can be found at http://mkweb.bcgsc.ca/colorblind/.\r\n\r\nFacilities:
CXO - Chandra X-ray Observatory satellite (ACIS), HST - Hubble Space Telescope satellite
(ACS, WFC3) - , CFHT - Canada-France-Hawaii Telescope (WIRCam), JWST - James Webb
Space Telescope (NIRSpec), Spitzer - Spitzer Space Telescope satellite (IRAC, MIPS)
- , JCMT - James Clerk Maxwell Telescope (SCUBA).\r\n\r\nSoftware: Astropy (Astropy
Collaboration et al. 2013, 2018, 2022), dust_attenuation, dust_extinction (K. Gordon
2024), jax (J. Bradbury et al. 2018), LaTeX (L. Lamport 1994), Matplotlib (J. D.
Hunter 2007), NumPy (T. E. Oliphant 2006; S. van der Walt et al. 2011; C. R. Harris
et al. 2020), NumPyro (D. Phan et al. 2019), scipy (P. Virtanen et al. 2020), sedpy
(B. Johnson & J. Leja 2017), specutils (Astropy-Specutils Development Team 2019),
unite (R. E. Hviding 2025)."
article_number: L18
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Raphael E.
full_name: Hviding, Raphael E.
last_name: Hviding
- first_name: Anna
full_name: De Graaff, Anna
last_name: De Graaff
- first_name: Hanpu
full_name: Liu, Hanpu
last_name: Liu
- first_name: Andy D.
full_name: Goulding, Andy D.
last_name: Goulding
- first_name: Yilun
full_name: Ma, Yilun
last_name: Ma
- first_name: Jenny E.
full_name: Greene, Jenny E.
last_name: Greene
- first_name: Leindert A.
full_name: Boogaard, Leindert A.
last_name: Boogaard
- first_name: Andrew J.
full_name: Bunker, Andrew J.
last_name: Bunker
- first_name: Nikko J.
full_name: Cleri, Nikko J.
last_name: Cleri
- first_name: Marijn
full_name: Franx, Marijn
last_name: Franx
- first_name: Michaela
full_name: Hirschmann, Michaela
last_name: Hirschmann
- first_name: Joel
full_name: Leja, Joel
last_name: Leja
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: David J.
full_name: Setton, David J.
last_name: Setton
- first_name: Hannah
full_name: Übler, Hannah
last_name: Übler
- first_name: Giacomo
full_name: Venturi, Giacomo
last_name: Venturi
- first_name: Bingjie
full_name: Wang, Bingjie
last_name: Wang
citation:
ama: 'Hviding RE, De Graaff A, Liu H, et al. The X-ray dot: Exotic dust or a late-stage
Little Red Dot? The Astrophysical Journal Letters. 2026;1000(1). doi:10.3847/2041-8213/ae4c88'
apa: 'Hviding, R. E., De Graaff, A., Liu, H., Goulding, A. D., Ma, Y., Greene, J.
E., … Wang, B. (2026). The X-ray dot: Exotic dust or a late-stage Little Red Dot?
The Astrophysical Journal Letters. IOP Publishing. https://doi.org/10.3847/2041-8213/ae4c88'
chicago: 'Hviding, Raphael E., Anna De Graaff, Hanpu Liu, Andy D. Goulding, Yilun
Ma, Jenny E. Greene, Leindert A. Boogaard, et al. “The X-Ray Dot: Exotic Dust
or a Late-Stage Little Red Dot?” The Astrophysical Journal Letters. IOP
Publishing, 2026. https://doi.org/10.3847/2041-8213/ae4c88.'
ieee: 'R. E. Hviding et al., “The X-ray dot: Exotic dust or a late-stage
Little Red Dot?,” The Astrophysical Journal Letters, vol. 1000, no. 1.
IOP Publishing, 2026.'
ista: 'Hviding RE, De Graaff A, Liu H, Goulding AD, Ma Y, Greene JE, Boogaard LA,
Bunker AJ, Cleri NJ, Franx M, Hirschmann M, Leja J, Matthee JJ, Naidu RP, Setton
DJ, Übler H, Venturi G, Wang B. 2026. The X-ray dot: Exotic dust or a late-stage
Little Red Dot? The Astrophysical Journal Letters. 1000(1), L18.'
mla: 'Hviding, Raphael E., et al. “The X-Ray Dot: Exotic Dust or a Late-Stage Little
Red Dot?” The Astrophysical Journal Letters, vol. 1000, no. 1, L18, IOP
Publishing, 2026, doi:10.3847/2041-8213/ae4c88.'
short: R.E. Hviding, A. De Graaff, H. Liu, A.D. Goulding, Y. Ma, J.E. Greene, L.A.
Boogaard, A.J. Bunker, N.J. Cleri, M. Franx, M. Hirschmann, J. Leja, J.J. Matthee,
R.P. Naidu, D.J. Setton, H. Übler, G. Venturi, B. Wang, The Astrophysical Journal
Letters 1000 (2026).
date_created: 2026-04-12T22:01:48Z
date_published: 2026-03-20T00:00:00Z
date_updated: 2026-05-04T07:13:07Z
day: '20'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.3847/2041-8213/ae4c88
external_id:
arxiv:
- '2601.09778'
file:
- access_level: open_access
checksum: 1be4f361bf59aa08b8c98ed4f475a463
content_type: application/pdf
creator: dernst
date_created: 2026-05-04T07:11:37Z
date_updated: 2026-05-04T07:11:37Z
file_id: '21784'
file_name: 2026_AstrophysicalJourLetters_Hviding.pdf
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has_accepted_license: '1'
intvolume: ' 1000'
issue: '1'
language:
- iso: eng
month: '03'
oa: 1
oa_version: Published Version
publication: The Astrophysical Journal Letters
publication_identifier:
eissn:
- 2041-8213
issn:
- 2041-8205
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'The X-ray dot: Exotic dust or a late-stage Little Red Dot?'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 1000
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
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PlanS_conform: '1'
_id: '21715'
abstract:
- lang: eng
text: New populations of red active galactic nuclei (known as “little red dots”)
discovered by JWST exhibit remarkable spectral energy distributions. Leveraging
X-ray through far-infrared observations of two of the most luminous known little
red dots, we directly measure their bolometric luminosities. We find evidence
that more than half of the bolometric luminosity likely emerges in the rest-frame
optical, with Lbol/L5100 = 5, roughly half the value for “standard” active galactic
nuclei. Meanwhile, the X-ray emitting corona, UV-emitting blackbody, and reprocessed
mid to far-infrared emission are all considerably subdominant, assuming that the
far-infrared luminosity is well below current measured limits. We present new
bolometric corrections that dramatically lower inferred bolometric luminosities
by a factor of 10 compared to published values in the literature. These bolometric
corrections are in accord with expectations from models in which gas absorption
and reprocessing are responsible for the red rest-frame optical colors of little
red dots. We discuss how this lowered luminosity scale suggests a lower mass scale
for the population by at least an order of magnitude (e.g., ∼105–107 M⊙ black
holes, and ∼108 M⊙ galaxies), alleviating tensions with clustering, overmassive
black holes, and the integrated black hole mass density in the Universe.
acknowledgement: "We benefit from the following JWST programs: UNCOVER (JWST/GO #2561;
Labbé & Bezanson); ALT (JWST-GO #3516; Naidu & Matthee); MegaScience (JWST-GO #4111;
Suess); RUBIES (JWST-GO #4233; de Graaff & Brammer); PRIMER (JWST/GO #1837; Dunlop).\r\n\r\nWe
acknowledge funding from NSF/AAG #2306950, JWST-GO-02561, JWST-GO-03516, and JWST-GO-04111,
provided through a grant from the STScI under NASA contract NAS5-03127. I.L. acknowledges
support from Australian Research Council Future Fellowship FT220100798. K.G. and
T.N. acknowledge support from Australian Research Council Laureate Fellowship FL180100060.
A.Z. acknowledges support by grant No. 2020750 from the United States-Israel Binational
Science Foundation (BSF) and grant No. 2109066 from the United States National Science
Foundation (NSF); by the Ministry of Science & Technology, Israel; and by the Israel
Science Foundation grant No. 864/23. J.M. and I.K. are funded by the European Union
(ERC, AGENTS, 101076224). Views and opinions expressed are, however, those of the
author(s) only and do not necessarily reflect those of the European Union or the
European Research Council. Neither the European Union nor the granting authority
can be held responsible for them. Y.F. acknowledges support from JSPS KAKENHI grant
No. JSPS KAKENHI grant Nos. JP22K21349 and JP23K13149. This work has received funding
from the Swiss State Secretariat for Education, Research and Innovation (SERI) under
contract No. MB22.00072, as well as from the Swiss National Science Foundation (SNSF)
through project grant 200020_207349. The Cosmic Dawn Center (DAWN) is funded by
the Danish National Research Foundation under grant DNRF140. Support for this work
for RPN was provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51515.001-A
awarded by the Space Telescope Science Institute, which is operated by the Association
of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.
The work of CCW is supported by NOIRLab, which is managed by the Association of
Universities for Research in Astronomy (AURA) under a cooperative agreement with
the National Science Foundation. J.M. acknowledges funding by the European Union
(ERC, AGENTS, 101076224). R.E.H. acknowledges support by the German Aerospace Center
(DLR) and the Federal Ministry for Economic Affairs and Energy (BMWi) through program
50OR2403 “RUBIES.”"
article_number: '129'
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Jenny E.
full_name: Greene, Jenny E.
last_name: Greene
- first_name: David J.
full_name: Setton, David J.
last_name: Setton
- first_name: Lukas J.
full_name: Furtak, Lukas J.
last_name: Furtak
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: Marta
full_name: Volonteri, Marta
last_name: Volonteri
- first_name: Pratika
full_name: Dayal, Pratika
last_name: Dayal
- first_name: Ivo
full_name: Labbe, Ivo
last_name: Labbe
- first_name: Pieter
full_name: Van Dokkum, Pieter
last_name: Van Dokkum
- first_name: Rachel
full_name: Bezanson, Rachel
last_name: Bezanson
- first_name: Gabriel
full_name: Brammer, Gabriel
last_name: Brammer
- first_name: Sam E.
full_name: Cutler, Sam E.
last_name: Cutler
- first_name: Karl
full_name: Glazebrook, Karl
last_name: Glazebrook
- first_name: Anna
full_name: De Graaff, Anna
last_name: De Graaff
- first_name: Michaela
full_name: Hirschmann, Michaela
last_name: Hirschmann
- first_name: Raphael E.
full_name: Hviding, Raphael E.
last_name: Hviding
- first_name: Vasily
full_name: Kokorev, Vasily
last_name: Kokorev
- first_name: Joel
full_name: Leja, Joel
last_name: Leja
- first_name: Hanpu
full_name: Liu, Hanpu
last_name: Liu
- first_name: Yilun
full_name: Ma, Yilun
last_name: Ma
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Themiya
full_name: Nanayakkara, Themiya
last_name: Nanayakkara
- first_name: Pascal A.
full_name: Oesch, Pascal A.
last_name: Oesch
- first_name: Richard
full_name: Pan, Richard
last_name: Pan
- first_name: Sedona H.
full_name: Price, Sedona H.
last_name: Price
- first_name: Justin S.
full_name: Spilker, Justin S.
last_name: Spilker
- first_name: Bingjie
full_name: Wang, Bingjie
last_name: Wang
- first_name: John R.
full_name: Weaver, John R.
last_name: Weaver
- first_name: Katherine E.
full_name: Whitaker, Katherine E.
last_name: Whitaker
- first_name: Christina C.
full_name: Williams, Christina C.
last_name: Williams
- first_name: Adi
full_name: Zitrin, Adi
last_name: Zitrin
citation:
ama: 'Greene JE, Setton DJ, Furtak LJ, et al. What you see is what you get: Empirically
measured bolometric luminosities of Little Red Dots. The Astrophysical Journal.
2026;996(2). doi:10.3847/1538-4357/ae1836'
apa: 'Greene, J. E., Setton, D. J., Furtak, L. J., Naidu, R. P., Volonteri, M.,
Dayal, P., … Zitrin, A. (2026). What you see is what you get: Empirically measured
bolometric luminosities of Little Red Dots. The Astrophysical Journal.
IOP Publishing. https://doi.org/10.3847/1538-4357/ae1836'
chicago: 'Greene, Jenny E., David J. Setton, Lukas J. Furtak, Rohan P. Naidu, Marta
Volonteri, Pratika Dayal, Ivo Labbe, et al. “What You See Is What You Get: Empirically
Measured Bolometric Luminosities of Little Red Dots.” The Astrophysical Journal.
IOP Publishing, 2026. https://doi.org/10.3847/1538-4357/ae1836.'
ieee: 'J. E. Greene et al., “What you see is what you get: Empirically measured
bolometric luminosities of Little Red Dots,” The Astrophysical Journal,
vol. 996, no. 2. IOP Publishing, 2026.'
ista: 'Greene JE, Setton DJ, Furtak LJ, Naidu RP, Volonteri M, Dayal P, Labbe I,
Van Dokkum P, Bezanson R, Brammer G, Cutler SE, Glazebrook K, De Graaff A, Hirschmann
M, Hviding RE, Kokorev V, Leja J, Liu H, Ma Y, Matthee JJ, Nanayakkara T, Oesch
PA, Pan R, Price SH, Spilker JS, Wang B, Weaver JR, Whitaker KE, Williams CC,
Zitrin A. 2026. What you see is what you get: Empirically measured bolometric
luminosities of Little Red Dots. The Astrophysical Journal. 996(2), 129.'
mla: 'Greene, Jenny E., et al. “What You See Is What You Get: Empirically Measured
Bolometric Luminosities of Little Red Dots.” The Astrophysical Journal,
vol. 996, no. 2, 129, IOP Publishing, 2026, doi:10.3847/1538-4357/ae1836.'
short: J.E. Greene, D.J. Setton, L.J. Furtak, R.P. Naidu, M. Volonteri, P. Dayal,
I. Labbe, P. Van Dokkum, R. Bezanson, G. Brammer, S.E. Cutler, K. Glazebrook,
A. De Graaff, M. Hirschmann, R.E. Hviding, V. Kokorev, J. Leja, H. Liu, Y. Ma,
J.J. Matthee, T. Nanayakkara, P.A. Oesch, R. Pan, S.H. Price, J.S. Spilker, B.
Wang, J.R. Weaver, K.E. Whitaker, C.C. Williams, A. Zitrin, The Astrophysical
Journal 996 (2026).
date_created: 2026-04-12T22:01:50Z
date_published: 2026-01-10T00:00:00Z
date_updated: 2026-05-04T11:20:42Z
day: '10'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.3847/1538-4357/ae1836
external_id:
arxiv:
- '2509.05434'
file:
- access_level: open_access
checksum: 7b3cb025d4bcaa35c6e52bd0c8fb6cf4
content_type: application/pdf
creator: dernst
date_created: 2026-05-04T11:19:48Z
date_updated: 2026-05-04T11:19:48Z
file_id: '21792'
file_name: 2026_AstrophysicalJour_Greene.pdf
file_size: 684400
relation: main_file
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file_date_updated: 2026-05-04T11:19:48Z
has_accepted_license: '1'
intvolume: ' 996'
issue: '2'
language:
- iso: eng
month: '01'
oa: 1
oa_version: Published Version
project:
- _id: bd9b2118-d553-11ed-ba76-db24564edfea
grant_number: '101076224'
name: Young galaxies as tracers and agents of cosmic reionization
publication: The Astrophysical Journal
publication_identifier:
eissn:
- 1538-4357
issn:
- 0004-637X
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'What you see is what you get: Empirically measured bolometric luminosities
of Little Red Dots'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 996
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
PlanS_conform: '1'
_id: '21846'
abstract:
- lang: eng
text: 'We compile a sample of 83 little red dots (LRDs) with JWST imaging and find
that a substantial fraction (∼43%, rising to ≳80% for the most luminous LRDs)
host one or more spatially offset, UV-bright companions at projected separations
of 0.5 kpc ≲ d ≲ 5 kpc, with median 〈d〉 = 1.0 kpc. This fraction is even higher
when smaller spatial scales are probed at high signal-to-noise ratio: the two
most strongly lensed LRDs, A383-LRD1 and the newly discovered A68-LRD1, both have
UV-bright companions at separations of only d ∼ 0.3 kpc, below the resolution
limit of most unlensed JWST samples. We explore whether these ubiquitous red/blue
configurations may be physically linked to the formation of LRDs, in analogy with
the “synchronized pair” scenario originally proposed for direct-collapse black
hole formation. In this picture, UV radiation from the companions, with typically
modest stellar masses (M∗ ∼ 108−109 M⊙), suppresses molecular hydrogen cooling
in nearby gas, allowing nearly isothermal collapse and the formation of extremely
compact objects, such as massive black holes, supermassive stars, or quasi-stars.
Using component-resolved photometry and spectral energy distribution modeling,
we infer Lyman–Werner radiation fields of J21,LW ∼ 102.5–105 at the locations
of the red components, comparable to those required in direct-collapse models,
suggesting that the necessary photodissociation conditions are realized in many
LRD systems. This framework provides a simple and self-consistent explanation
for the extreme compactness and distinctive spectral properties of LRDs and links
long-standing theoretical models for early compact object formation directly to
a population now observed with JWST in the early Universe.'
acknowledgement: 'We thank Earl Bellinger, Fabio Pacucci, Andrea Ferrara, and Dale
Kocevski for useful discussions. This work is based on observations made with the
NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski
Archive for Space Telescopes at the Space Telescope Science Institute, which is
operated by the Association of Universities for Research in Astronomy, Inc., under
NASA contract NAS 5-03127 for JWST. These imaging observations are associated with
programs 1345, 1180, 1181, 1243, 6882, 2561, 1324, 4111, and 1895. The compiled
dataset can be accessed at doi:10.17909/1m8f-9c47. The Cosmic Dawn Center (DAWN)
is funded by the Danish National Research Foundation under grant DNRF140. J.M. and
A.T. acknowledge funding by the European Union (ERC, AGENTS, 101076224). This work
was performed in part at Aspen Center for Physics, which is supported by National
Science Foundation grant PHY-2210452. This work used the following Python packages:
Matplotlib (J. D. Hunter 2007), SciPy (P. Virtanen et al. 2020), NumPy (S. van der
Walt et al. 2011), AstroPy (Astropy Collaboration et al. 2022), colossus (B. Diemer
2018), and photutils (L. Bradley et al. 2025).'
article_number: L4
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Josephine F.W.
full_name: Baggen, Josephine F.W.
last_name: Baggen
- first_name: Matthew T.
full_name: Scoggins, Matthew T.
last_name: Scoggins
- first_name: Pieter
full_name: Van Dokkum, Pieter
last_name: Van Dokkum
- first_name: Zoltán
full_name: Haiman, Zoltán
id: 7c006e8c-cc0d-11ee-8322-cb904ef76f36
last_name: Haiman
orcid: 0000-0003-3633-5403
- first_name: Alberto
full_name: Torralba Torregrosa, Alberto
id: 018f0249-0e87-11f0-b167-cbce08fbd541
last_name: Torralba Torregrosa
orcid: 0000-0001-5586-6950
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
citation:
ama: 'Baggen JFW, Scoggins MT, Van Dokkum P, Haiman Z, Torralba Torregrosa A, Matthee
JJ. Connecting the dots: UV-bright companions of Little Red Dots as Lyman–Werner
sources enabling direct-collapse Black Hole formation. The Astrophysical Journal
Letters. 2026;1002(1). doi:10.3847/2041-8213/ae58a5'
apa: 'Baggen, J. F. W., Scoggins, M. T., Van Dokkum, P., Haiman, Z., Torralba Torregrosa,
A., & Matthee, J. J. (2026). Connecting the dots: UV-bright companions of
Little Red Dots as Lyman–Werner sources enabling direct-collapse Black Hole formation.
The Astrophysical Journal Letters. IOP Publishing. https://doi.org/10.3847/2041-8213/ae58a5'
chicago: 'Baggen, Josephine F.W., Matthew T. Scoggins, Pieter Van Dokkum, Zoltán
Haiman, Alberto Torralba Torregrosa, and Jorryt J Matthee. “Connecting the Dots:
UV-Bright Companions of Little Red Dots as Lyman–Werner Sources Enabling Direct-Collapse
Black Hole Formation.” The Astrophysical Journal Letters. IOP Publishing,
2026. https://doi.org/10.3847/2041-8213/ae58a5.'
ieee: 'J. F. W. Baggen, M. T. Scoggins, P. Van Dokkum, Z. Haiman, A. Torralba Torregrosa,
and J. J. Matthee, “Connecting the dots: UV-bright companions of Little Red Dots
as Lyman–Werner sources enabling direct-collapse Black Hole formation,” The
Astrophysical Journal Letters, vol. 1002, no. 1. IOP Publishing, 2026.'
ista: 'Baggen JFW, Scoggins MT, Van Dokkum P, Haiman Z, Torralba Torregrosa A, Matthee
JJ. 2026. Connecting the dots: UV-bright companions of Little Red Dots as Lyman–Werner
sources enabling direct-collapse Black Hole formation. The Astrophysical Journal
Letters. 1002(1), L4.'
mla: 'Baggen, Josephine F. W., et al. “Connecting the Dots: UV-Bright Companions
of Little Red Dots as Lyman–Werner Sources Enabling Direct-Collapse Black Hole
Formation.” The Astrophysical Journal Letters, vol. 1002, no. 1, L4, IOP
Publishing, 2026, doi:10.3847/2041-8213/ae58a5.'
short: J.F.W. Baggen, M.T. Scoggins, P. Van Dokkum, Z. Haiman, A. Torralba Torregrosa,
J.J. Matthee, The Astrophysical Journal Letters 1002 (2026).
date_created: 2026-05-10T22:02:15Z
date_published: 2026-04-10T00:00:00Z
date_updated: 2026-05-11T06:48:33Z
day: '10'
ddc:
- '520'
department:
- _id: ZoHa
- _id: JoMa
doi: 10.3847/2041-8213/ae58a5
external_id:
arxiv:
- '2602.02702'
file:
- access_level: open_access
checksum: 8c31d8603cd6ad39c772a72d136dc3f8
content_type: application/pdf
creator: dernst
date_created: 2026-05-11T06:44:37Z
date_updated: 2026-05-11T06:44:37Z
file_id: '21851'
file_name: 2026_AstrophysicalJourLetters_Baggen.pdf
file_size: 13359642
relation: main_file
success: 1
file_date_updated: 2026-05-11T06:44:37Z
has_accepted_license: '1'
intvolume: ' 1002'
issue: '1'
language:
- iso: eng
month: '04'
oa: 1
oa_version: Published Version
project:
- _id: bd9b2118-d553-11ed-ba76-db24564edfea
grant_number: '101076224'
name: Young galaxies as tracers and agents of cosmic reionization
publication: The Astrophysical Journal Letters
publication_identifier:
eissn:
- 2041-8213
issn:
- 2041-8205
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'Connecting the dots: UV-bright companions of Little Red Dots as Lyman–Werner
sources enabling direct-collapse Black Hole formation'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 1002
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
PlanS_conform: '1'
_id: '21882'
abstract:
- lang: eng
text: The nature of little red dots (LRDs) has largely been investigated through
their continuum emission, with lines assumed to arise from a broad-line region.
In this paper, we instead use recombination lines to infer the intrinsic properties
of the central engine. Our analysis first reveals a tension between the ionizing
properties implied from Hα and He ii λ4686. The high Hα EWs require copious H-ionizing
photons, more than the bluest active galactic nucleus (AGN) ionizing spectra can
provide. In contrast, He ii emission is marginally detected, and its low EW is,
at most, consistent with the softest AGN spectra. The low He ii/Hβ (∼10−2, <20× local
AGN median) further points to an unusually soft ionizing spectrum. We extend our
analysis to dense gas envelopes (quasi-star/black-hole star) and find that hydrogen
recombination lines become optically thick and lose diagnostic power, but He ii
remains optically thin and a robust tracer. Photoionization modeling with Cloudy
rules out standard AGN accretion disk spectra. Alternative explanations include
exotic AGN with red rest-optical emission, high average optical depth (>10) from
gas/dust, and soft ionizing spectra with abundant H-ionizing photons, consistent
with, e.g., a cold accretion disk or a composite of AGN and stars. The latter
is an intriguing scenario since high hydrogen densities are highly conducive for
star formation, and nuclear star clusters are found in the vicinity of local massive
black holes. While previous studies have mostly focused on features dominated
by the absorbing hydrogen cloud, the He ii-based diagnostic proposed here represents
a crucial step toward understanding the central engine of LRDs.
acknowledgement: "B.W. thanks Michael Eracleous for valuable discussions. B.W. and
J.L. acknowledge support from JWST-GO-04233.009. B.W. also acknowledges support
provided by NASA through Hubble Fellowship grant HST-HF2-51592.001 awarded by the
Space Telescope Science Institute, which is operated by the Association of Universities
for Research in Astronomy, Inc., for NASA, under the contract NAS 5-26555. K.I.
acknowledges support from the National Natural Science Foundation of China (12573015,
W2532003), the Beijing Natural Science Foundation (IS25003), and the China Manned
Space Program (CMS-CSST-2025-A09). R.E.H. acknowledges support by the German Aerospace
Center (DLR) and the Federal Ministry for Economic Affairs and Energy (BMWi) through
program 50OR2403 “RUBIES.”\r\n\r\nThis work is based on observations made with the
NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski
Archive for Space Telescopes at the Space Telescope Science Institute, which is
operated by the Association of Universities for Research in Astronomy, Inc., under
NASA contract NAS 5-03127 for JWST. These observations are associated with program
# 1433, 2561, 4106, 4233, 5224, 6585. The specific observations analyzed can be
accessed via DOI: 10.17909/9hpc-nc45. Computations for this research were performed
on the Pennsylvania State University’s Institute for Computational and Data Sciences’
Roar supercomputer; and on computational resources managed and supported by Princeton
Research Computing, a consortium of groups including the Princeton Institute for
Computational Science and Engineering (PICSciE) and Research Computing at Princeton
University. Some of the stellar spectra are retrieved from the POLLUX database (pollux.oreme.org)
operated at LUPM (Université de Montpellier—CNRS, France) with the support of the
PNPS and INSU. This publication made use of the NASA Astrophysical Data System for
bibliographic information."
article_number: '10'
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Bingjie
full_name: Wang, Bingjie
last_name: Wang
- first_name: Joel
full_name: Leja, Joel
last_name: Leja
- first_name: Harley
full_name: Katz, Harley
last_name: Katz
- first_name: Kohei
full_name: Inayoshi, Kohei
last_name: Inayoshi
- first_name: Nikko J.
full_name: Cleri, Nikko J.
last_name: Cleri
- first_name: Anna
full_name: De Graaff, Anna
last_name: De Graaff
- first_name: Raphael E.
full_name: Hviding, Raphael E.
last_name: Hviding
- first_name: Pieter
full_name: Van Dokkum, Pieter
last_name: Van Dokkum
- first_name: Jenny E.
full_name: Greene, Jenny E.
last_name: Greene
- first_name: Ivo
full_name: Labbé, Ivo
last_name: Labbé
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Ian
full_name: Mcconachie, Ian
last_name: Mcconachie
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: Erica J.
full_name: Nelson, Erica J.
last_name: Nelson
citation:
ama: 'Wang B, Leja J, Katz H, et al. The missing hard photons of Little Red Dots:
Their incident ionizing spectra resemble massive stars. The Astrophysical Journal.
2026;1003(1). doi:10.3847/1538-4357/ae5bab'
apa: 'Wang, B., Leja, J., Katz, H., Inayoshi, K., Cleri, N. J., De Graaff, A., …
Nelson, E. J. (2026). The missing hard photons of Little Red Dots: Their incident
ionizing spectra resemble massive stars. The Astrophysical Journal. IOP
Publishing. https://doi.org/10.3847/1538-4357/ae5bab'
chicago: 'Wang, Bingjie, Joel Leja, Harley Katz, Kohei Inayoshi, Nikko J. Cleri,
Anna De Graaff, Raphael E. Hviding, et al. “The Missing Hard Photons of Little
Red Dots: Their Incident Ionizing Spectra Resemble Massive Stars.” The Astrophysical
Journal. IOP Publishing, 2026. https://doi.org/10.3847/1538-4357/ae5bab.'
ieee: 'B. Wang et al., “The missing hard photons of Little Red Dots: Their
incident ionizing spectra resemble massive stars,” The Astrophysical Journal,
vol. 1003, no. 1. IOP Publishing, 2026.'
ista: 'Wang B, Leja J, Katz H, Inayoshi K, Cleri NJ, De Graaff A, Hviding RE, Van
Dokkum P, Greene JE, Labbé I, Matthee JJ, Mcconachie I, Naidu RP, Nelson EJ. 2026.
The missing hard photons of Little Red Dots: Their incident ionizing spectra resemble
massive stars. The Astrophysical Journal. 1003(1), 10.'
mla: 'Wang, Bingjie, et al. “The Missing Hard Photons of Little Red Dots: Their
Incident Ionizing Spectra Resemble Massive Stars.” The Astrophysical Journal,
vol. 1003, no. 1, 10, IOP Publishing, 2026, doi:10.3847/1538-4357/ae5bab.'
short: B. Wang, J. Leja, H. Katz, K. Inayoshi, N.J. Cleri, A. De Graaff, R.E. Hviding,
P. Van Dokkum, J.E. Greene, I. Labbé, J.J. Matthee, I. Mcconachie, R.P. Naidu,
E.J. Nelson, The Astrophysical Journal 1003 (2026).
date_created: 2026-05-17T22:02:10Z
date_published: 2026-05-01T00:00:00Z
date_updated: 2026-05-18T08:18:39Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.3847/1538-4357/ae5bab
external_id:
arxiv:
- '2508.18358'
file:
- access_level: open_access
checksum: ee9ebc8ae2304fec04f24b82ebaac8bc
content_type: application/pdf
creator: dernst
date_created: 2026-05-18T08:17:26Z
date_updated: 2026-05-18T08:17:26Z
file_id: '21891'
file_name: 2026_AstrophysicalJourn_Wang.pdf
file_size: 2584417
relation: main_file
success: 1
file_date_updated: 2026-05-18T08:17:26Z
has_accepted_license: '1'
intvolume: ' 1003'
issue: '1'
language:
- iso: eng
month: '05'
oa: 1
oa_version: Published Version
publication: The Astrophysical Journal
publication_identifier:
eissn:
- 1538-4357
issn:
- 0004-637X
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'The missing hard photons of Little Red Dots: Their incident ionizing spectra
resemble massive stars'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 1003
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
PlanS_conform: '1'
_id: '21898'
abstract:
- lang: eng
text: We investigate the nature and spectroscopic diversity of early galaxies from
a sample of 41 sources at $z\geqslant 10$ with James Webb Space Telescope (JWST)/NIRSpec
prism observations. We compare the properties of strong ultraviolet (UV) line
emitters, traced by intense C iv emission, with those of more ‘typical’ sources
with weak or undetected C iv. The more typical (or ‘C iv-weak’) sources reveal
significant scatter in their C iii] line strengths, UV continuum slopes, and physical
sizes, spanning C iii] equivalent widths (EWs) of $\sim$1–51 Å, UV slopes of $\beta
\sim -1.6$ to $-2.6$, and half-light radii of $\sim$50–1000 pc. In contrast, C iv-strong
sources occupy the tail of these distributions, with C iii] EWs of 16–51 Å, UV
slopes $\beta \lesssim -2.5$, compact morphologies ($r_{\rm 50} \lesssim 100$ pc),
and elevated star formation surface densities ($\Sigma _{\rm SFR} \gtrsim 100\,
M_\odot \, \mathrm{yr}^{-1}\, \mathrm{kpc}^{-2}$). These properties suggest concentrated
starbursts that temporarily outshine the host galaxy. Comparing average properties
from composite spectra, we find the diversity of the sample is primarily driven
by bursty star formation on very short time-scales ($\le$3 Myr), with strong C iv
emitters observed at the apex of the bursts and sources devoid of emission lines
during relative inactivity. An apparent association between strong C iv and enhanced
nitrogen abundance suggests both may be modulated by the same duty cycle, reflecting
a generic mode of star formation. We show that active galactic nuclei are unlikely
to contribute significantly to this duty cycle based on UV line diagnostics and
photoionization models. Our results support a picture whereby brief bursts and
lulls can explain the spectral diversity and early growth of bright galaxies in
the first 500 Myr.
acknowledgement: "We thank the anonymous referee for useful and constructive\r\nfeedback
that improved the manuscript. GRB is grateful to Vasily\r\nBelokurov and Sarah Kane
for providing the relevant abundances\r\nforthe Aurora data in Fig. 11, as well
asto Tiger Yu-Yang Hsiao for\r\nhelpful discussions regarding the MACS 0647-JD source.
We are\r\nalso grateful to Gabe Brammerfor useful discussions and his continuous
efforts in maintaining and improving the msaexp code,\r\nfrom which the high-z community
continues to benefit greatly.\r\nLastly, we also thank the numerous teams of the
observational\r\nprograms used in this study, for developing these valuable data\r\nsets.
The data used in this study are derived from the following\r\nprograms: 1181 (PI
Eisenstein; D. J. Eisenstein et al. 2023a), 1210\r\n(PI Luetzgendorf; D. J. Eisenstein
et al. 2023a), 1211 (PI Isaak;\r\nM. V. Maseda et al. 2024), 1286 (PI Luetzgendorf;
D. J. Eisenstein\r\net al. 2023a), 1287 (PI Isaak; D. J. Eisenstein et al. 2023a),
1345\r\n(PI Finkelstein; S. L. Finkelstein et al. 2025), 1433 (PI Coe; T. Y.-\r\nY.
Hsiao et al. 2024a), 2561 (PI Labbé; R. Bezanson et al. 2022),\r\n2750 (PI Arrabal
Haro; P. Arrabal Haro et al. 2023b), 3073 (PI\r\nCastellano; M. Castellano et al.
2024), 3215 (PIs Eisenstein &\r\nMaiolino; D. J. Eisenstein et al. 2023b), 5224
(PIs Oesch & Naidu;\r\nOesch et al. in preparation), 6368 (PI Dickinson; V. Kokorev
et al.\r\n2025). The authors acknowledge the aforementioned teams and\r\nPIs where
development of their observing program(s) was done\r\nwith a zero-exclusive-access
period.\r\nThis work is based on observations made with the\r\nNASA/ESA/CSA JWST.
The data were obtained from the\r\nMikulski Archive for Space Telescopes at the
Space Telescope\r\nScience Institute, which is operated by the Association of\r\nUniversities
for Research in Astronomy, Inc., under NASA\r\ncontract NAS 5-03127 for JWST. The
specific observations\r\nanalysed can be accessed via DOI 10.17909/jqj3-ws37. Some\r\nof
the data products presented herein were retrieved from the\r\nDawn JWST Archive
(DJA). DJA is an initiative of the Cosmic\r\nDawn Center (DAWN), which is funded
by the Danish National\r\nResearch Foundation under grant DNRF140.\r\nRSE acknowledges
generous financial support from the Peter\r\nand Patricia Gruber Foundation. YF
acknowledgessupportsfrom\r\nJSPS KAKENHI Grant Numbers JP22K21349 and JP23K13149.\r\nThis
work has received funding from the Swiss State Secretariat\r\nfor Education, Research
and Innovation (SERI) under contract\r\nnumber MB22.00072, as well as from the Swiss
National Science\r\nFoundation (SNSF) through project grant 200020_207349."
article_number: stag701
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Guido
full_name: Roberts-Borsani, Guido
last_name: Roberts-Borsani
- first_name: Pascal A
full_name: Oesch, Pascal A
last_name: Oesch
- first_name: Richard
full_name: Ellis, Richard
last_name: Ellis
- first_name: Andrea
full_name: Weibel, Andrea
last_name: Weibel
- first_name: Emma
full_name: Giovinazzo, Emma
last_name: Giovinazzo
- first_name: Rychard
full_name: Bouwens, Rychard
last_name: Bouwens
- first_name: Pratika
full_name: Dayal, Pratika
last_name: Dayal
- first_name: Adriano
full_name: Fontana, Adriano
last_name: Fontana
- first_name: Kasper E
full_name: Heintz, Kasper E
last_name: Heintz
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Romain A
full_name: Meyer, Romain A
last_name: Meyer
- first_name: Laura
full_name: Pentericci, Laura
last_name: Pentericci
- first_name: Alice
full_name: Shapley, Alice
last_name: Shapley
- first_name: Sandro
full_name: Tacchella, Sandro
last_name: Tacchella
- first_name: Tommaso
full_name: Treu, Tommaso
last_name: Treu
- first_name: Fabian
full_name: Walter, Fabian
last_name: Walter
- first_name: Hakim
full_name: Atek, Hakim
last_name: Atek
- first_name: Sownak
full_name: Bose, Sownak
last_name: Bose
- first_name: Marco
full_name: Castellano, Marco
last_name: Castellano
- first_name: Yoshinobu
full_name: Fudamoto, Yoshinobu
last_name: Fudamoto
- first_name: Takahiro
full_name: Morishita, Takahiro
last_name: Morishita
- first_name: Rohan P
full_name: Naidu, Rohan P
last_name: Naidu
- first_name: Ryan L
full_name: Sanders, Ryan L
last_name: Sanders
- first_name: Arjen
full_name: van der Wel, Arjen
last_name: van der Wel
citation:
ama: 'Roberts-Borsani G, Oesch PA, Ellis R, et al. JWST spectroscopic insights into
the diversity of galaxies in the first 500 Myr: Short-lived snapshots along a
common evolutionary pathway. Monthly Notices of the Royal Astronomical Society.
2026;548(3). doi:10.1093/mnras/stag701'
apa: 'Roberts-Borsani, G., Oesch, P. A., Ellis, R., Weibel, A., Giovinazzo, E.,
Bouwens, R., … van der Wel, A. (2026). JWST spectroscopic insights into the diversity
of galaxies in the first 500 Myr: Short-lived snapshots along a common evolutionary
pathway. Monthly Notices of the Royal Astronomical Society. Oxford University
Press. https://doi.org/10.1093/mnras/stag701'
chicago: 'Roberts-Borsani, Guido, Pascal A Oesch, Richard Ellis, Andrea Weibel,
Emma Giovinazzo, Rychard Bouwens, Pratika Dayal, et al. “JWST Spectroscopic Insights
into the Diversity of Galaxies in the First 500 Myr: Short-Lived Snapshots along
a Common Evolutionary Pathway.” Monthly Notices of the Royal Astronomical Society.
Oxford University Press, 2026. https://doi.org/10.1093/mnras/stag701.'
ieee: 'G. Roberts-Borsani et al., “JWST spectroscopic insights into the diversity
of galaxies in the first 500 Myr: Short-lived snapshots along a common evolutionary
pathway,” Monthly Notices of the Royal Astronomical Society, vol. 548,
no. 3. Oxford University Press, 2026.'
ista: 'Roberts-Borsani G, Oesch PA, Ellis R, Weibel A, Giovinazzo E, Bouwens R,
Dayal P, Fontana A, Heintz KE, Matthee JJ, Meyer RA, Pentericci L, Shapley A,
Tacchella S, Treu T, Walter F, Atek H, Bose S, Castellano M, Fudamoto Y, Morishita
T, Naidu RP, Sanders RL, van der Wel A. 2026. JWST spectroscopic insights into
the diversity of galaxies in the first 500 Myr: Short-lived snapshots along a
common evolutionary pathway. Monthly Notices of the Royal Astronomical Society.
548(3), stag701.'
mla: 'Roberts-Borsani, Guido, et al. “JWST Spectroscopic Insights into the Diversity
of Galaxies in the First 500 Myr: Short-Lived Snapshots along a Common Evolutionary
Pathway.” Monthly Notices of the Royal Astronomical Society, vol. 548,
no. 3, stag701, Oxford University Press, 2026, doi:10.1093/mnras/stag701.'
short: G. Roberts-Borsani, P.A. Oesch, R. Ellis, A. Weibel, E. Giovinazzo, R. Bouwens,
P. Dayal, A. Fontana, K.E. Heintz, J.J. Matthee, R.A. Meyer, L. Pentericci, A.
Shapley, S. Tacchella, T. Treu, F. Walter, H. Atek, S. Bose, M. Castellano, Y.
Fudamoto, T. Morishita, R.P. Naidu, R.L. Sanders, A. van der Wel, Monthly Notices
of the Royal Astronomical Society 548 (2026).
date_created: 2026-05-20T14:34:29Z
date_published: 2026-05-01T00:00:00Z
date_updated: 2026-05-21T06:16:04Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1093/mnras/stag701
external_id:
arxiv:
- '2508.21708'
file:
- access_level: open_access
checksum: b8f52c6fc5e06b3a505310e7d5898ecf
content_type: application/pdf
creator: dernst
date_created: 2026-05-21T06:14:23Z
date_updated: 2026-05-21T06:14:23Z
file_id: '21902'
file_name: 2026_MNRAS_RobertsBorsani.pdf
file_size: 3539140
relation: main_file
success: 1
file_date_updated: 2026-05-21T06:14:23Z
has_accepted_license: '1'
intvolume: ' 548'
issue: '3'
language:
- iso: eng
month: '05'
oa: 1
oa_version: Published Version
publication: Monthly Notices of the Royal Astronomical Society
publication_identifier:
eissn:
- 1365-2966
issn:
- 0035-8711
publication_status: published
publisher: Oxford University Press
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'JWST spectroscopic insights into the diversity of galaxies in the first 500
Myr: Short-lived snapshots along a common evolutionary pathway'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 548
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
PlanS_conform: '1'
_id: '21930'
abstract:
- lang: eng
text: "We present the discovery of extreme nitrogen enrichment by Wolf Rayet nitrogen
(WN) stars in the metal-poor (∼10%Z⊙), lensed, compact (Reff ∼ 20 pc) galaxy RXCJ2248
at z = 6.1, revealed by unprecedentedly deep\r\nJWST/NIRSpec medium-resolution
spectroscopy from the GLIMPSE-D Survey. The exquisite signal-to-noise\r\nratio
reveals multiple high-ionization nebular lines and broad Balmer and [O III] components
(FWHM\r\n∼700–3000 km s\r\n−1\r\n). We detect broadened He II λ1640 and λ4687
(FWHM ∼ 530 km s\r\n−1\r\n) and strong N III λ4642\r\nemission consistent with
a population of WN stars, making RXCJ2248 the most distant galaxy with confirmed\r\nWolf
Rayet (WR) features to date. We measure the multiphase nebular density across
five ions, the direct-method\r\nmetallicity (\r\n12 + log(O/H) = 7.753 ± 0.025\r\n),
and a nonuniform elemental enrichment pattern of extreme N/O\r\nenhancement (\r\nlog(N/O)
= 0.391 ± 0.037\r\nfrom N+, N+2\r\n, and N+3\r\n) but suppressed C/O relative
to empirical\r\nC/N trends. We show that this abundance pattern can be explained
by enrichment from a dual-burst with a low\r\nWR carbon/WN ratio, as expected
at low metallicities. Crucially, these signatures can only arise during a brief,\r\nrare
evolutionary window shortly after a burst (∼3–6 Myr), when WN stars dominate chemical
feedback but\r\nbefore dilution by later yields (e.g., supernovae). The observed
frequency of strong N emitters at high−z implies a\r\n∼50 Myr burst duty cycle,
suggesting that N/O outliers may represent a brief but ubiquitous phase in the\r\nevolution
of highly star-forming early galaxies. The WN detection in RXCJ2248, therefore,
provides the first\r\ndirect evidence of WR-driven nitrogen enrichment in the
first billion years of the Universe and a novel timing\r\nargument for the bursty
star formation cycles that shaped galaxies at cosmic dawn."
acknowledgement: "\r\nThe American Astronomical Society, find out more.\r\n\r\nThe
following article isOpen access\r\nA Fleeting GLIMPSE of N/O Enrichment at Cosmic
Dawn: Evidence for Wolf Rayet N Stars in a z = 6.1 Galaxy\r\nDanielle A. Berg, Rohan
P. Naidu, John Chisholm, Hakim Atek, Seiji Fujimoto, Vasily Kokorev, Lukas J. Furtak,
Chiaki Kobayashi, Daniel Schaerer, Angela Adamo, Qinyue Fei, Damien Korber, Jorryt
Matthee, Rui Marques-Chaves, Zorayda Martinez, Kristen. B. W. McQuinn, Julian B.
Muñoz, Pascal A. Oesch, Alberto Saldana-Lopez, Daniel P. Stark, Mabel G. Stephenson,
and Tiger Yu-Yang HsiaoHide full author list\r\n\r\nPublished 2026 May 20 • © 2026.
The Author(s). Published by the American Astronomical Society.\r\nThe Astrophysical
Journal, Volume 1003, Number 2\r\nCitation Danielle A. Berg et al 2026 ApJ 1003
112\r\nDOI 10.3847/1538-4357/ae5e4c\r\n\r\nDownloadArticle PDFDownloadArticle ePub\r\nAuthors\r\nFigures\r\nTables\r\nReferences\r\nArticle
data\r\nDownload PDFDownload ePub\r\nArticle metrics\r\n173 Total downloads\r\n\r\nShare
this article\r\nArticle information\r\nAbstract\r\nWe present the discovery of extreme
nitrogen enrichment by Wolf Rayet nitrogen (WN) stars in the metal-poor (∼10%Z⊙),
lensed, compact (Reff ∼ 20 pc) galaxy RXCJ2248 at z = 6.1, revealed by unprecedentedly
deep JWST/NIRSpec medium-resolution spectroscopy from the GLIMPSE-D Survey. The
exquisite signal-to-noise ratio reveals multiple high-ionization nebular lines and
broad Balmer and [O iii] components (FWHM ∼700–3000 km s−1). We detect broadened
He ii λ1640 and λ4687 (FWHM ∼ 530 km s−1) and strong N iii λ4642 emission consistent
with a population of WN stars, making RXCJ2248 the most distant galaxy with confirmed
Wolf Rayet (WR) features to date. We measure the multiphase nebular density across
five ions, the direct-method metallicity (\r\n), and a nonuniform elemental enrichment
pattern of extreme N/O enhancement (\r\n from N+, N+2, and N+3) but suppressed C/O
relative to empirical C/N trends. We show that this abundance pattern can be explained
by enrichment from a dual-burst with a low WR carbon/WN ratio, as expected at low
metallicities. Crucially, these signatures can only arise during a brief, rare evolutionary
window shortly after a burst (∼3–6 Myr), when WN stars dominate chemical feedback
but before dilution by later yields (e.g., supernovae). The observed frequency of
strong N emitters at high−z implies a ∼50 Myr burst duty cycle, suggesting that
N/O outliers may represent a brief but ubiquitous phase in the evolution of highly
star-forming early galaxies. The WN detection in RXCJ2248, therefore, provides the
first direct evidence of WR-driven nitrogen enrichment in the first billion years
of the Universe and a novel timing argument for the bursty star formation cycles
that shaped galaxies at cosmic dawn.\r\n\r\nExport citation and abstract\r\nBibTeXRIS\r\n\r\nPrevious
article in issue\r\nNext article in issue\r\n\r\nOriginal content from this work
may be used under the terms of the Creative Commons Attribution 4.0 licence. Any
further distribution of this work must maintain attribution to the author(s) and
the title of the work, journal citation and DOI.\r\n\r\n1. Introduction\r\nA key
tracer of galaxy evolution is the change in their chemical composition over time.
The metallicity of a galaxy is a sensitive observational diagnostic of its past
star formation history and present-day evolutionary state given that metallicity
increases with each successive generation of massive star yields (e.g., M. Tosi
1988; J.-R. Roy & D. Kunth 1995; D. A. Berg et al. 2019; R. Maiolino & F. Mannucci
2019). Oxygen is an important tracer of metallicity because it is the most abundant
element in the Universe after H and He and is convenient to observe, with ubiquitous
emission lines from H ii regions in the rest-frame optical regime. While O emission
in dwarf and spiral galaxies has been widely observed in the rest-frame optical
and UV (e.g., R. C. Kennicutt 1992; Y. I. Izotov & T. X. Thuan 1999; L. van Zee
& M. Haynes2006; D. A. Berg et al. 2012, 2016, 2019; P. Senchyna et al. 2017; N.
S. J. Rogers et al. 2022), the N emission in these same galaxies has been predominantly
traced only in the optical through the low-ionization [N ii] λλ6550,6585 emission
lines. In general, there is a surprising dearth of detections of the high-ionization
N emission counterparts in local galaxies, totaling less than 10 galaxies with significant
detections of either N iv] λλ1483,1486 or N iii] λ1750 (e.g., M. Mingozzi et al.
2022; Z. Martinez et al. 2025). However, with the advent of JWST, there is a growing
prevalence of z ≳ 5 galaxies with extreme properties, including intense UV N emission
(e.g., A. J. Bunker et al. 2023; Y. Isobe et al. 2023; M. Castellano et al. 2024;
T. Y.-Y. Hsiao et al. 2024; X. Ji et al. 2024; R. Marques-Chaves et al. 2024; D.
Schaerer et al. 2024; M. Curti et al. 2025a; Y. Harikane et al. 2025a; R. P. Naidu
et al. 2026; M. W. Topping et al. 2025b).\r\n\r\nThe first noted, and one of the
most distant, examples of extreme rest-frame UV N emission comes from the spectroscopically
confirmed z = 10.6 galaxy, GN-z11. JWST spectra of GN-z11 revealed surprisingly
strong N iv] λλ1483,1486 and N iii] λ1750 emission (e.g., A. J. Bunker et al. 2023)
that corresponds to supersolar nitrogen-to-oxygen (N/O) enrichment (\r\n; e.g.,
A. J. Cameron et al. 2023). Subsequently, enhanced N/O has been reported in a number
of high−z galaxies, including GDS 3073 (z = 5.55; X. Ji et al. 2024), RXCJ2248-ID
(z = 6.10; M. W. Topping et al. 2024), A1703-zd6 (z = 7.04; M. W. Topping et al.
2025b), CEERS-1019 (z = 8.68; R. Marques-Chaves et al. 2024), GNz9p4 (z = 9.38;
D. Schaerer et al. 2024), GHZ9 (z = 10.15; L. Napolitano et al. 2025), GHZ2 (z =
12.34; M. Castellano et al. 2024), and MoM-z14 (z = 14.44; R. P. Naidu et al. 2026).
For a review of nitrogen line detections, see D. P. Stark et al. (2025). Such strong
nebular N+3 emission requires a relatively hard ionizing radiation field (≳47.4
eV), where models of massive stars predict few photons. On the other hand, N+2 has
a lower ionization potential (∼29.6 eV), but statistically significant detections
are strikingly rare in integrated galaxy spectra (e.g., D. A. Berg et al. 2018;
M. Mingozzi et al. 2022; A. J. Bunker et al. 2023; P. Senchyna et al. 2024) and
are only expected to be strong at the highest possible nebular temperatures (∼2.5
× 104 K). Furthermore, the timing of the incredibly high N/O abundances reported
for the high-redshift UV N emitters just a few 100 Myr after the Big Bang is unexpected.\r\n\r\nThe
discovery of significant, rapid nitrogen enhancement so early in the Universe was
surprising because it contradicts our longstanding understanding of N production.
In typical chemical evolution modeling, some nitrogen enrichment can occur early
on via core collapse supernova (CCSN), but substantial nitrogen enrichment only
occurs 100 s of megayears after the onset of star formation via asymptotic giant
branch (AGB) stars (e.g., F. Vincenzo et al. 2019; C. Kobayashi et al. 2020). Thus,
alternative, faster enrichment methods are needed to explain substantial nitrogen
enrichment in early galaxies. As a result, the necessary ionizing flux and conditions
to produce the unexpectedly strong N+3 and N+2 emission observed in galaxies beyond
z ∼ 5 have been attributed to more extreme sources, such as active galactic nuclei
(AGN; R. Maiolino et al. 2024), Wolf Rayet (WR) stars (e.g., P. Senchyna et al.
2024; K. Watanabe et al. 2024; M. L. P. Gunawardhana et al. 2025), globular cluster
precursors (e.g., C. Charbonnel et al. 2023; X. Ji et al. 2026), super star clusters
(e.g., M. Pascale et al. 2023), very massive stars (VMSs: M⋆ > 102 M⊙; e.g., J.
S. Vink 2023; Y. Shi et al. 2026), or supermassive stars (M⋆ > 103 M⊙; e.g., C.
Charbonnel et al. 2023; C. Nagele & H. Umeda 2023), tidal disruption events (e.g.,
A. J. Cameron et al. 2023; K. Watanabe et al. 2024), and more.\r\n\r\nMost of our
understanding of WR stars has been built from observations of individual resolved
stars in a handful of galaxies in the Local Group, with almost no direct spectroscopic
evidence for the prevalence of WR stars in more distant galaxies. To date, only
two systems at Cosmic Noon (z ≈ 2–3) have confirmed signatures of WR stars: MARTA-4327
at z = 2.224 (hereafter, M4327; M. Curti et al. 2025b) and the Sunburst Arc at z
= 2.37 (T. E. Rivera-Thorsen et al. 2024). Extending such detections to earlier
cosmic epochs is crucial for understanding the role of massive stars in shaping
the chemical evolution of galaxies in the first Gyr.\r\n\r\nHere, we investigate
the z = 6.1 lensed galaxy RXCJ2248-ID3. RXCJ2248-ID was first identified by F. Boone
et al. (2013), I. Balestra et al. (2013), and A. Monna et al. (2014) and discovered
to be a high-ionization, compact, metal-poor, N-enhanced galaxy by R. Mainali et
al. (2017), K. B. Schmidt et al. (2017), and M. W. Topping et al. (2024). We present
extremely deep JWST/NIRSpec observations of RXCJ2248-ID3 that provide the highest-redshift
spectroscopic evidence of WR nitrogen (WN) stars to date, which provide a physically
consistent mechanism driving its extreme nitrogen enrichment (M. W. Topping et al.
2024). The remainder of this paper is organized as follows. The observations and
data reduction are briefly described in Section 2.1, followed by a description of
the emission-line fits, including the broad lines related to the WR feedback, in
Section 2.2. We present the discovery of WN stars at z ∼ 6 via their spectral signatures
in Section 3. We determine new nebular properties and O, C, N, and Si abundances
in Section 4.3 and compare them to populations of both low- and high-redshift galaxies.
We discuss the source of N enrichment in the early Universe and subsequently estimate
mass production and timing arguments in Section 5. Finally, we present our conclusions
in Section 6. Throughout this work, we adopt cosmological parameters of H0 = 70
km s−1 Mpc−1, Ωm = 0.30, and ΩΛ = 0.7 and the solar abundance pattern from M. Asplund
et al. (2021).\r\n\r\n2. JWST/NIRSpec Spectra\r\nRXCJ2248 is a galaxy at z ∼ 6.1
that is lensed into multiple images by the Abell S1063 cluster (α = 22:48:44.13,
δ =−44:31:57.50) at a redshift of z = 0.348. We present an analysis of the brightest
image, RXCJ2248-ID3 (J = 25.0), which has a magnification of μ ∼ 7 (L. Furtak et
al. 2025). RXCJ2248-ID was discovered as a z ∼ 6 candidate (F. Boone et al. 2013;
A. Monna et al. 2014) using the 16-band HST photometry of the CLASH Survey and spectroscopically
confirmed via VIsible Multi-Object Spectrograph (VIMOS)/VLT observations by I. Balestra
et al. (2013). RXCJ2248-ID3 was soon found to be an exciting extreme emission-line
galaxy via ground-based spectroscopy (R. Mainali et al. 2017), with strong detections
of high-ionization emission such as O iii] λλ1661,1666 and C ivλλ1548,1550 but no
He ii, suggesting star formation as the ionizing source rather than an AGN.\r\n\r\nThe
early spectra of RXCJ2248-ID3 motivated further rest-UV+optical study with JWST/NIRSpec
by M. W. Topping et al. (2024). This work performed direct metallicity calculations
to show that RXCJ2248-ID3 is one of the most extreme N/O-enhanced (), metal-poor
() galaxies, with high-ionization ([O iii] λ5008/[O ii] λ3728 = 184) and high nebular
density (6.4 × 104 ≤ ne(cm−3) ≤3.1 × 105). They also used spectral energy distribution
(SED) fitting with a constant star formation history to characterize its low stellar
mass (M⋆ ∼ 108 M⊙) and the young-massive star population (∼2 Myr) of RXCJ2248. M.
W. Topping et al. (2024), therefore, suggest that the N/O enrichment may be due
to a short-lived phase that many z > 6 bursty galaxies experience. In this paper,
we build on the work of M. W. Topping et al. (2024) with new, extraordinarily deep
rest-optical JWST/NIRSpec observations of RXCJ2248-ID3 from the GLIMPSE-D Survey,
a Director’s Discretionary Time (DDT) follow-up program described below.\r\n\r\n2.1.
Observations and Reduction\r\nThe work presented here uses both the rest-UV JWST/NIRSpec
archival spectra from JWST PID 2478 (PI Stark) and new rest-optical JWST/NIRSpec
spectra from the GLIMPSE-D Survey, which is an extension of the GLIMPSE Survey.
Properties of RXCJ2248-ID and observation details are presented in Table 1.\r\n\r\nTable
1. Properties of RXCJ2248-ID3\r\n\r\nJWST/NIRSpec Observations\r\nGrating/Filter\t(s)\tPI/PID\r\nG140M/F100LP\t6215\tStark/2478\r\nG235M/F170LP\t1576\tStark/2478\r\nG395M/F290LP\t107,228\tFujimoto
& Naidu/9223\r\nMeasured Properties\r\nProperty\tValue\tReferences\r\nR.A.\t+22:48:45.81\tThis
work\r\nDecl.\t−44:32:14.95\tThis work\r\nz\t6.1025 ± 0.0013\tThis work\r\nμ\t6.8877\tL.
Furtak et al. (2025)\r\nReff (pc)\t\tA. Claeyssens (2025)\r\nM⋆ (M⊙)\t\tA. Claeyssens
(2025)\r\nΣ⋆ (M⊙ pc−2)\t\tA. Claeyssens (2025)\r\nSFRHα (M⊙ yr−1)\t3.2\tThis work,
Section 5.3\r\nSFRSED,1Myr\t4.7\tA. Claeyssens (2025)\r\nSFRSED,10Myr\t4.1\tA. Claeyssens
(2025)\r\nΣSFR (M⊙ yr−1 kpc−2)\t1.34 × 103\tThis work\r\ntage (Myr)\t\tA. Claeyssens
(2025)\r\n12+log(O/H)\t7.753 ± 0.025\tThis work, Section 4.3.1\r\nlog(N/O)\t−0.391
± 0.037\tThis work, Section 4.3.2\r\nNote. Top: JWST/NIRSpec observations of RXCJ2248-ID3,
including archival observations from PID 2478 (PI: Stark) and very deep GLIMPSE-D
observations from PID 9223 (PI: Fujimoto & Naidu). Columns (1)–(3) list the grating/filter,
exposure time, and principle investigator/PID. Bottom: Measured global properties
of RXCJ2248-ID3. The R.A. and decl. are the extraction coordinates for RXCJ2248-ID3.
The redshift was determined from the GLIMPSE-D spectrum emission lines. GLIMPSE
imaging was used to determine the lensing model magnification, μ. Effective radius
of the RXCJ2248-ID3 clump, stellar mass, and current massive star population age
are from the SED modeling of A. Claeyssens (2025), while the SFR was determined
from both the SED fitting and the narrow-component, collisions-corrected Hα flux
(see Section 5.3), all corrected for the lensing factor. The star formation rate
surface density was determined using the SFRHα. The metallicity and relative N/O
abundance were determined using the direct method.\r\n\r\nDownload table as: \r\nASCIITypeset
image\r\n\r\nThe GLIMPSE Survey is a large Cycle 2 JWST program (PID 3293; PIs Atek
& Chisholm) that performed ultradeep NIRCam imaging (∼30.8 mag at 5σ over 0.8–5
μm) in seven broadband and two medium-band filters of the lensing cluster Abell
S1063 (H. Atek et al. 2025). A. Claeyssens (2025) performed size and photometric
measurements of RXCJ2248-ID in the different multiple images. The SED fitting was
performed with the Bayesian Analysis of Galaxies for Physical Inference and Parameter
Estimation (BAGPIPES; A. C. Carnall et al. 2018) code with Binary Population and
Spectral Synthesis (BPASS v2.14, J. J. Eldridge et al. 2017) stellar population
synthesis burst models and cloudy v23.01 photoionization models (M. Chatzikos et
al. 2023; C. M. Gunasekera et al. 2023). Priors were used to be physically consistent
with the source, i.e., high-ionization parameter (), low extinction (Av < 0.5 mag),
low metallicity (Z < 0.4 Z⊙), and bursty star formation (τ = 1 Myr, i.e., close
to a single burst, or τ = 10 Myr). The resulting best fit has a young age ( Myr)
and low stellar mass of but within a compact size of pc such that the stellar mass
surface density is . This value is akin to the highest densities found in globular
clusters, similar to the ones reported for young star clusters and clumps at high
redshift (A. Claeyssens et al. 2025; M. Messa et al. 2026), and broadly consistent
with the conclusions presented in M. W. Topping et al. (2024).\r\n\r\nSubsequent
medium-resolution (R ∼ 1000) spectra of RXCJ2248-ID3 were obtained as part of the
follow-up GLIMPSE-D Survey: JWST DDT Program 9223 (PIs Fujimoto & Naidu) targeting
a Pop III candidate in S. Fujimoto et al. (2025) using NIRSpec Multi-Object Spectroscopy
(MOS) with the G395M grating and F290LP filter. As part of this program, RXCJ2248-ID3
was observed for a total of 13 exposures using a 3-point nod pattern and NRSIRS2
readout, totaling ∼30 hr of integration. The MSA slit positions covering RXCJ2248-ID3
of the three pointings are shown in Figure 1.\r\n\r\nZoom InZoom OutReset image
size\r\nFigure 1. JWST/NIRSpec MSA slits targeting RXCJ2248-ID3 for each of the
three exposures in the GLIMPSE-D program. The two pointings that are closely aligned
(solid purple regions) have the same wavelength coverage, while the pointing offset
to the lower left (dashed region) has somewhat reduced blue coverage. All three
pointings were used in the spectrum coaddition.\r\n\r\nDownload figure:\r\n\r\nStandard
imageHigh-resolution image\r\nWe augment the rest-optical GLIMPSE-D data with archival
rest-far-UV G140M/F100LP and rest-near-UV G235M/F170LP observations from PID 2478
(PI Stark), covering the rest-frame ∼1400–4000 Å range. This program also observed
the G395M/F290LP setting, but we only use the significantly deeper GLIMPSE-D G395M
observations here. Multiple images of RXCJ2248 were identified and observed in program
#2478. M. W. Topping et al. (2024) utilized these data by coadding the spectra of
the individual images. In contrast, only the brightest image (ID3) was observed
in the GLIMPSE-D Survey. To ensure consistency, we therefore restricted our analysis
to the G140M and G235M spectra of ID3 obtained in program #2478. As a result, our
G140M and G235M measurements are not directly comparable to those presented by M.
W. Topping et al. (2024).\r\n\r\nThe data were reduced using v0.9.8 of the msaexp
pipeline (G. Brammer 2022), following the standard routines described in A. de Graaff
et al. (2025), K. E. Heintz et al. (2025), and F. Valentino et al. (2025). Briefly,
level-2 calibrated products from MAST are subject to a series of custom corrections
that account for, e.g., 1/f noise, bar vignetting, and detector bias. We used the
“local” nodded background subtraction. The 2D spectra were drizzled onto a common
wavelength grid and 1D spectra were optimally extracted using a profile model that
accounts for, e.g., the wavelength-dependent PSF and offsets from the nominal position
expected from the catalog. Line centers were measured for the strongest emission
lines in the G395M spectrum (i.e., Hδ, Hγ, [O iii] λ4364, Hβ, [O iii] λλ4960,5008,
He iλ5877, Hα, He iλ7067) and used to determine a redshift of z = 6.1025 ± 0.0013.
Note that the bluest portion of the G395M tends to favor a slightly lower redshift
(i.e., z ∼ 6.1000), while the reddest portion favors a slightly higher redshift
(i.e., z ∼ 6.1034). The three individual 1D extracted spectra were then normalized
to the common continuum flux scale of the first spectrum at rest-wavelengths of
∼6000–62000 Å prior to coadding. Spectral coaddition was performed as a weighted
average using the inverse variance as the weight.\r\n\r\nThe resulting spectrum,
shown in Figure 2, covers an observed wavelength range ∼2.8–5.5 μm, which corresponds
to a rest-optical range of ∼3900–7740 Å. Note that the third pointing (dashed slits
in Figure 1) has reduced wavelength coverage such that the blue end begins at ∼4265.
The deep GLIMPSE-D spectra provide unparalleled signal-to-noise ratio (S/N; >5 at
5100 Å continuum) that enable rest-optical diagnostics typically reserved for nearby
galaxies.\r\n\r\nZoom InZoom OutReset image size\r\nFigure 2. JWST/NIRSpec rest-frame
UV and optical spectra of RXCJ2248-ID3 highlighting the first object known with
simultaneously detected emission from N+, N+2, and N+3 (see, also, M. W. Topping
et al. 2024) and WR features. The second row shows the main emission UV emission-line
detections from the archival G140M/F100LP spectrum, with significant detections
of several high-ionization emission lines, including N iv] λλ1483,1486, C iv λλ1548,1550,
He ii λ1640, O iii] λλ1661,1666, N iii] λ1750, and C iii] λλ1907,1909. The third
row shows the blue end of the optical spectrum, where the left-hand panel shows
the archival G235M/F170LP spectrum, which includes the low-ionization [O ii] λλ3727,3730
doublet. The right-hand panel of the third row and the fourth row shows the extremely
high S/N GLIMPSE-D optical spectrum, enabling detections of several weak features.
Note that some of the important features to this work are highlighted in the zoom
in panels in the top row. In particular, the last panel reveals the most distant
WR detection to date, with the λ4650 WR bump showing emission from N iii λ4642,
indicative of nitrogen enrichment from WN stars. Note that not all of the labeled
lines correspond to line detections.\r\n\r\nDownload figure:\r\n\r\nStandard imageHigh-resolution
image\r\n2.2. Emission-line Measurements\r\nIn order to perform a consistent analysis
of our data, we measure emission-line fluxes for both the archival spectra and the
new GLIMPSE-D spectra presented here. We fit neighboring emission lines simultaneously
using Gaussian profiles with the lmfit package (M. Newville et al. 2015) in Python.
Purely nebular lines (i.e., lines without possible stellar contributions or resonant
effects) close in wavelengths were constrained to have the same full width at half-maximum
(FWHM) velocity widths. Additionally, the relative wavelength spacing between lines
was constrained to laboratory values and doublets with constant flux ratios set
by atomic physics were constrained to their theoretical values, with small uncertainty
allowances. The uncertainties on the line fluxes were estimated as the standard
error derived from the least-squares minimization in lmfit, which considers the
uncertainty on the Gaussian profile and linear continuum.\r\n\r\nBroad emission
components are clearly visible at the base of some of the emission lines in the
GLIMPSE-D spectrum of RXCJ2248-ID3. Such broad emission features can be produced
by stellar winds, shocks, or turbulence. Since He iiλ1640 and λ4687 emission lines
can be affected by stellar winds, we fit these features with an unconstrained Gaussian
width. Using the jwst-msa package (A. de Graaff et al. 2024), we deconvolved all
measured FWHMs with the modeled wavelength-dependent line spread function (LSF).
We found the He ii lines to be broadened compared to purely nebular lines. For the
He iiλ 4687 line, the velocity width is 528 ± 100 km s−1, which is more than two
times broader than the narrow nebular Hβ component with vFWHM = 243 ± 25 km s−1.\r\n\r\nThe
strongest rest-optical H (Hγ, Hβ, and Hα) and [O iii] (λ4364, λλ4960,5008) emission
lines have complex profiles with both narrow and broad emission components. Such
broad components may also be present in the rest-UV and fainter rest-optical emission
lines, but none are obvious given the lower S/N of these emission features and/or
underlying continuum. To fit these profiles, we tested three different multicomponent
profile combination fits for the Hα + [N ii] complex. For all three fits, the narrow
Hα and [N ii] λλ6550,6585 lines were fit by Gaussians with a single velocity width,
but the broad component was fit with either: (1) a single Gaussian profile, (2)
two Gaussian profiles, or (3) a single exponential profile. The single broad Gaussian
profile fit had strong residuals near the center of the broad component, so did
not provide a good fit to the observed emission profile. Both the double Gaussian
profile and the exponential profile provided relatively good visual fits, but the
double Gaussian fit had a lower reduced chi-squared ( vs ) and Bayesian inference
criteria (BIC2Gauss = 36 versus (BICexp. = 87), and so was adopted as the better
statistical fit.\r\n\r\nThe right panel of Figure 3 shows the best multicomponent
fit to the Hα + [N ii] complex. Since all kinematically similar lines in the Balmer
emission series arise from the same gas, we expect the Hβ and Hγ profiles to be
well fit by scaling the Hα best fit. Therefore, we constrained the velocity widths
of the Hβ and Hγ emission components to match the narrow + double broad Gaussian
Hα fit, accounting for the wavelength-dependent LSF. We found excellent fit results,
with similarly small reduced-χ2 and BIC values. This means that the H i lines are
well fit by a profile with (1) a strong, narrow (∼250 km s−1) nebular component,
(2) a moderate (∼20% of total flux), broad component (∼670 km s−1), and (3) a weak
(∼10% of total flux), very broad (∼2530 km s−1) component.\r\n\r\nZoom InZoom OutReset
image size\r\nFigure 3. Multicomponent emission-line fits to the GLIMPSE spectrum
of RXCJ2248-ID for Hα λ6565 + [N II] λλ6549,6585 (left panels), Hβ λ4863 + [O III]
λλ4960,5008 (middle panels), and Hγ λ4342 + [O III] λ4364 (right panels). When fit
with single, narrow Gaussian components (e.g., purple and yellow filled Gaussians),
all three line complexes show strong, broad component residual flux. The resulting
best fit to each line is comprised of a single narrow Gaussian plus two broad Gaussians,
where the relevant component velocity widths are tied together: The Hα λ6565 + [N
ii] λλ6549,6585 complex fit provided the velocity width constraints for the H Balmer
line narrow (purple Gaussians) and broad components (blue and green Gaussians) and,
subsequently, the Hβ λ4863 + [O iii] λλ4960,5008 fit constrained the [O iii] narrow
(yellow Gaussian) and broad (orange and red Gaussians) velocity widths that were
then used in the Hγ λ4342 + [O iii] λ4364 fit. Note that additional faint lines
(e.g., He i λ5017) were included in the fit in the middle panel. Careful accounting
for the residual broad flux has a significant impact on the derived nebular reddening,
temperature, metallicity, and N/O abundance.\r\n\r\nDownload figure:\r\n\r\nStandard
imageHigh-resolution image\r\nThe [O iii] λλ4960,5008 doublet lines are also well
fit by a narrow Gaussian plus double Gaussian broad component profile, with the
relative fluxes of each component constrained to the theoretical ratio. While the
narrow-component FWHM was set to the velocity width of the narrow Balmer lines,
convolved with the LSF, we allowed the FWHM of the two broad [O iii] components
to vary freely and found widths of ∼890 km s−1 and ∼2980 km s−1, respectively. The
similarity between the [O iii] and H i velocity widths of the broad components argues
against emission from an AGN directly (where high densities cause collisional de-excitation
of [O iii]) and is more consistent with stellar or AGN driven winds (e.g., Y. I.
Izotov & T. X. Thuan 2008; G. Gräfener & J. S. Vink2015; G. Gräfener et al. 2017;
C. J. Burke et al. 2021). Interestingly, the broad components of the H i lines compose
a larger fraction of their total flux (∼20% and 10%, respectively) than [O iii]
(∼10% and 5%, respectively).\r\n\r\nThe resulting fit to the Hβ + [O iii] λλ4960,5008
complex is shown in the middle panel of Figure 3 to be an excellent fit, with minimal
residuals. The exquisite S/N of the GLIMPSE spectrum also reveals broad wings on
the [O iii] λ4364 profile, as seen in the left panel of Figure 3. Therefore, we
also applied the narrow Gaussian plus double Gaussian broad component profile to
[O iii] λ4364, constraining the velocity widths to the values measured for [O iii]
λλ4960,5008.\r\n\r\nDouble broad components with similar velocity widths (750 and
2500 km s−1, respectively) are seen in the z ∼ 0 extreme emission-line galaxies,
J1044+0353 and J1418+2102, reported in D. A. Berg et al. (2021). However, each broad
component observed in these nearby analogs only accounts for 1%–3% of the total
H i flux. This sort of broad component emission from the Balmer H and [O iii] lines
with widths (1000–2000 km s−1) and fractional fluxes of 1%–2% is commonly found
in spectra of blue compact dwarf galaxies (BCDs; e.g., Y. I. Izotov et al. 2006,
2007). This suggests that bulk motion of the gas is typical in these metal-poor,
bursty environments, but for a larger mass of gas in RXCJ2248-ID3.\r\n\r\nThe sensitive
accounting of broad component emission afforded by the deep GLIMPSE-D spectra is
important because even a small fraction of broad emission around H emission line
can significantly affect the fit to weak lines such as [N ii] λλ6550,6585 (e.g.,
D. A. Berg et al. 2021). In RXCJ2248-ID, the broad components compose a significant
fraction of the total H and [O iii] fluxes, and so are critical to properly measure
not only the [N ii] λ6585 emission but also the [O iii] λ4364, Hβ, [O iii] λλ4960,5008,
and Hα narrow-line fluxes. For this reason, we adopt the narrow-line fluxes from
our best multicomponent fits for the remaining analysis; we reserve further investigation
of the the broad emission for a forthcoming paper.\r\n\r\nAs noted above, the UV
spectra do not have sufficient S/N to decompose narrow and possible broad components.
As a result, density diagnostics and relative abundance ratios determined from UV
line ratios may include contributions from multiple kinematic components. If the
broad components arise from gas with distinct physical conditions, this could introduce
systematic offsets. We test the level of bias possible due to broad component contamination
of narrow-line fluxes by adopting the relative narrow and broad component profiles
of [O iii] λ5008 as a template for collisionally excited lines. The broad component
areas overlap with the narrow profile such that the broad components are responsible
for 8.6% and 2.2% of the narrow-component flux, or 10.8% in total. We use this fraction
to set the upper contamination limit of potential broad components to the UV emission
lines and determine the impact on nebular density, temperature, and abundance calculations
in Section 4.4.\r\n\r\n2.3. Reddening Correction\r\nThe observed Balmer decrement
of the narrow Hα/Hβ lines is FHα/FHβ = 3.48, implying either a moderate amount of
dust is present or collisional enhancement of Hα. This value disagrees with the
results of M. W. Topping et al. (2024), who measured an observed decrement of 2.55
± 0.05 that they found to be consistent with no dust attenuation. Similarly, A.
Crespo Gómez et al. (2025) used high-resolution NIRSpec/G395H data to fit multiple
component Balmer decrements for RXCJ2248-ID3, finding a narrow-component FHα/FHβ
= 2.7 that is consistent with no attenuation, but broad- and very broad-component
decrements of 4.3 and 6.6, respectively, that imply differential extinction. We
too find higher FHα/FHβ ratios for the broad components, but the source of this
increase is not clear; it could indicate higher dust in the broad component gas,
as suggested by A. Crespo Gómez et al. (2025), or result from significant collisional
enhancement of Hα.\r\n\r\nFortunately, the GLIMPSE-D spectrum provides a significant
increase in S/N in the continuum, allowing for more robust fitting of broad components,
including in the Hγ and [O iii] λ4364 and λ5008 lines. Fitting the broad components
directly in the [O iii] lines offers the advantage over previous works that we do
not need to correct for broad component contamination with differential extinction
in our Te calculation. Furthermore, by fitting the broad components in Hγ we were
able to examine the narrow-component Hβ/Hγ ratio, finding a decrement of FHβ/FHγ
= 2.16 that is consistent with very little dust (see Table 2). Note that we do not
consider the Hβ/Hδ ratio here because the Hδ line is not strong enough to robustly
fit the broad components in a consistent manner with the profile fitting of the
Hγ, Hβ, and Hα lines.\r\n\r\nTable 2. Rest UV+Optical Emission-Line Fluxes\r\n\r\nIon+Wavelength\tI(λ)/I(C
iii])\tEW\r\n(Å)\t \t(Å)\r\nN iv] λ1483.33\t42.78 ± 1.61\t6.67\r\nN iv] λ1486.50\t102.0
± 0.82\t15.9\r\nHe iiλ1640.42\t22.46 ± 197\t4.88\r\nO iii] λ1666.15\t85.84 ± 0.59\t18.9\r\nN
iii] λ1750a\t38.59 ± 0.64\t9.18\r\nSi iii] λ1883.00\t5.01 ± 3.25\t1.32\r\nSi iii]
λ1892.03\t8.25 ± 1.98\t2.21\r\nC iii] λ1906.68\t35.11 ± 0.31\t9.65\r\n[C iii] λ1908.73\t64.89
± 0.25\t17.9\r\nIon+Wavelength\tI(λ)/I(Hβ)\tEW\r\n(Å)\t \t(Å)\r\n[O ii] λ3728a\t4.09
± 2.05\t6.22\r\nHγ λ4341.66b\t47.41 ± 3.07\t73.8\r\n[O iii] λ4364.44b\t42.45 ± 1.92\t66.5\r\nHe
i λ4472.73\t8.90 ± 0.39\t27.8\r\nN iii λ4641.94\t1.40 ± 0.20\t4.4\r\nHe ii λ4687.01\t1.33
± 0.29\t4.2\r\n[Ar iv] λ4712.69c\t2.30 ± 0.27\t10.3\r\nHe i λ4714.46c\t1.91 ± 0.19\t3.0\r\n[Ar
iv] λ4741.49\t4.10 ± 0.26\t13.0\r\nHβ λ4862.71b\t100.0 ± 4.4\t356\r\n[O iii] λ4960.29b\t230.5
± 9.0\t877\r\n[O iii] λ5008.24b\t708.9 ± 27.5\t2791\r\nHα λ6564.60b,d\t331.8 ± 14.4\t1755\r\nHα
λ6564.60b,e\t274.1 ± 11.9\t1457\r\n[N ii] λ6585.27\t7.08 ± 0.91\t12.8\r\n[S ii]
λ6718.29\t0.68 ± 0.29\t4.78\r\n[S ii] λ6732.67\t0.81 ± 0.30\t4.74\r\nE(B − V)\t\t⋯\r\nFC
III]\t11.58 ± 0.49\t⋯\r\nb\t6.94 ± 0.15\t⋯\r\nNotes. Reddening-corrected emission-line
intensities of lines used in this analysis from the archival rest-UV and GLIMPSE
rest-optical JWST/NIRSpec spectra for RXCJ2248-ID3. Note that no scaling was performed
between the archival UV and GLIMPSE-D optical pointings (not needed for this work).
Thus, UV fluxes are given relative to the FC III]λλ1907,09 × 100 and optical fluxes
are given relative to FHβ × 100. The last three rows list the dust attenuation derived
using the J. A. Cardelli et al. (1989) reddening law and the rest-frame C iii] λλ1907,09
and Hβ flux in units of 10−18 erg s−1 cm−2. Additionally, the fluxes reported here
are for a single image of RXCJ2248 (ID3), whereas M. W. Topping et al. (2024) report
fluxes for coadded spectra of multiple images. aNote that N iii] λ1750 and [O ii]
λ3728 fluxes are the integrated values for the N iii] λλ1746,1748,1749,1752,1754
quintuplet and [O ii] λλ3727,3730 doublet, respectively. bEmission-line profile
was best fitted with a narrow Gaussian and two broad Gaussian components; only the
corrected narrow-line flux is listed here (see Section 2.2 and Figure 3). c[Ar iv]
λ4713+He iλ4714 is a blended line profile at the observed resolution. Thus, the
[Ar iv] λ4713 is determined by subtracting the He iλ4714 flux, which is predicted
from the He i λ4473 flux. dUncorrected for collisional excitation. eCorrected for
collisional excitation.\r\n\r\nDownload table as: \r\nASCIITypeset image\r\n\r\nThe
reddening due to dust, characterized by E(B − V), was determined by comparing the
observed Balmer decrements with the theoretical Balmer ratios assuming case B and
an extinction law, for which we tested the parameterization from both J. A. Cardelli
et al. (1989) and D. Calzetti et al. (2000). The E(B − V) value for a given Balmer
ratio was determined iteratively until convergence, recomputing the H i theoretical
ratio using the updated electron temperature from the reddening-corrected [O iii]
λ4364/λ5008 flux ratio and density from the reddening-corrected N iv] λ1483/λ1487
flux ratio in each iteration. In this way, the reddening, electron temperature,
and electron density were solved for simultaneously and consistently.\r\n\r\nA greater
enhancement of the observed FHα/FHβ decrement than of the FHβ/FHγ decrement can
arise under high-density conditions, where collisional excitation selectively enhances
the lowest excited level (n = 2; requires lowest energy to excite), leading to higher
Hα flux relative to Hβ and Hγ. To assess whether such an enhancement is physically
plausible, we examined the Cloudy photoionization models (M. Chatzikos et al. 2023;
C. M. Gunasekera et al. 2023) presented in Z. Martinez et al. (2025), which span
a wide range of nebular densities (up to ne = 109 cm−3). For the nebular conditions
determined in this work (i.e., Te, , Z, N/O; see Section 4), densities of ne ∼ 106
cm−3 are needed to produce the observed Hα enhancement while minimally affecting
Hβ and Hγ. Although this density is roughly an order of magnitude higher than the
values measured in M. W. Topping et al. (2024) and in this study (see Section 4.1
and Table 3), it could indicate that the interstellar medium (ISM) contains unresolved
clumps of even higher density than the volume-weighted values probed by the density
diagnostics used in this work. We, therefore, attribute the observed Hα excess to
collisional enhancement.\r\n\r\nTable 3. Nebular Conditions and Abundances for RXCJ2248-ID3\r\n\r\nProperty\tIon.
E\tUsed\tValue\r\n \t(eV)\t \t \r\nTemperatures:\t \t \r\nTe,high meas. (K)\t35.11–54.93\tne(N+3)\t1.97
± 0.03 × 104\r\nTe,int. used (K)\t23.33–34.83\tD. R. Garnett (1992)\t1.81 ± 0.02
× 104\r\nTe,low used (K)\t13.62–35.11\tD. R. Garnett (1992)\t1.68 ± 0.02 × 104\r\nDensities:\t
\t \t \r\nne(N+3) (cm−3)\t47.45–77.47\tTe,high\t\r\nne(Ar+3) (cm−3)\t40.74–59.81\tTe,high\t\r\nne(C+2)
(cm−3)\t24.38–47.89\tTe,int.\t\r\nne(Si+2) (cm−3)\t16.35–33.49\tTe,int.\t\r\nne(S+)
(cm−3)\t10.36–23.33\tTe,low\t\r\nO Abundances:\r\nO+/H+ (×10−5)\t13.62–35.11\tTe,low;
ne(Si+2)\t0.186 ± 0.148\r\nO+2/H+ (×10−5)\t35.11–54.93\tTe,high; ne(Ar+2)\t5.473
± 0.261\r\n \t \t7.753 ± 0.023\r\nIonization Parameters:\r\nlogUint.(O32)\t13.62–54.93\tne
= 104 cm−3\t−1.24 ± 0.23\r\nlogUhigh(N43)\t29.60–77.47\tne = 105 cm−3\t−0.69 ± 0.10\r\nN
Abundances:\r\nN+3/O+2\t47.45–77.47\tTe,high; ne(N+3)\t0.277 ± 0.043\r\nN+2/O+2\t29.60–47.45\tTe,high;
ne(C+2)\t0.145 ± 0.070\r\nN+/O+\t14.53–29.60\tTe,low; ne(Si+2)\t0.367 ± 0.259\r\nICF(N+3/O+2)\t47.45–77.47\tTe,high;
ne(N+3)\t1.542\r\nICF(N+2/O+2)\t29.60–47.45\tTe,high; ne(C+2)\t2.547\r\nICF(N+/O+)\t14.53–29.60\tTe,low;
ne(Si+2)\t0.814\r\nlog(N/O)\t⋯\t⋯\t−0.368 ± 0.062\r\nlog(N/O)\t⋯\t⋯\t−0.434 ± 0.071\r\nlog(N/O)\t⋯\t⋯\t−0.525
± 0.257\r\nlog(N/O)all\t⋯\t⋯\t−0.375 ± 0.056\r\n⋯\t⋯\t−0.390 ± 0.035\r\nC Abundance:\r\nC+2/O+2\t24.38–47.89\tTe,int;
ne(C+2)\t0.107 ± 0.014\r\nICF(C+2/O+2)\t24.38–47.89\tTe,int; ne(C+2)\t1.498\r\nlog(C/O)\t
\t \t−0.795 ± 0.052\r\nSi Abundance:\r\nSi+2/O+2\t16.35–33.49\tTe,low; ne(Si+2)\t0.005
± 0.001\r\nICF(Si+2/O+2)\t16.35–33.49\tTe,low; ne(Si+2)\t3.507\r\nlog(Si/O)\t⋯\t⋯\t−1.781
± 0.157\r\nNote. Ionic and total abundances for RXCJ2248-ID3. Column (1) lists the
property, while Column (2) lists the associated ionization potential energy range
(eV), Column (3) lists the temperature and/or density used in the calculation, and
Column (4) provides the final values. All calculations reported here only used the
narrow components when multicomponent fits were performed. Note that the temperatures
for the intermediate- and low-ionization zones were inferred from Te,high using
the Te–Te relationships of D. R. Garnett (1992). Two ionization parameters are reported
for the O32 and N43 indicators from Z. Martinez et al. (2025). The oxygen abundance
was determined using the archival [O ii] λ3728 detection and the new [O iii] λ5008
fit. N/O was determined using four different ion+ICF (from Z. Martinez et al. 2025)
combinations: (1) optical N+/O+; (2) UV N+2/O+2; (3) UV N+3/O+2; and (4) combination
(N++N+2+N+3)/(O++O+2). C/O and Si/O were determined from the archival UV emission
lines only.\r\n\r\nDownload table as: \r\nASCIITypeset image\r\n\r\nAccordingly,
we adopted the reddening derived from Hγ/Hβ, mag using J. A. Cardelli et al. (1989)
(the D. Calzetti et al. (2000) value is similar at E(B − V) = 0.050 ± 0.1215 mag),
and corrected all emission lines for the resulting (minimal) dust attenuation. We
used the D. Calzetti et al. (2000) reddening law for the rest-UV emission lines
(λ < 3200 Å) and the J. A. Cardelli et al. (1989) reddening law for the rest-optical
emission lines (λ > 3200 Å). After applying the reddening correction, the Hα/Hβ
ratio still shows a collisional excess of 0.204 above the theoretical value; we
correct for this excess and report a final FHα = 1.985 × 10−17 erg s−1 cm−2.\r\n\r\nThe
adopted reddening and dereddened line intensities are listed in Table 2 for all
line fluxes used in this work. Note that rest-UV and rest-optical lines should not
be compared or combined in line ratios. Since the rest-UV and rest-optical spectra
were obtained during different observing runs with distinct pointings and strategies,
we report the UV lines relative to FCIII]λλ1907,1909 × 100 and the optical lines
relative to FHβ × 100, without applying any relative scalings between the two datasets.\r\n\r\n3.
Wolf Rayet Stars at z = 6.1\r\nThe WR stage of massive star evolution is an important,
short-lived phase that can have significant effects on the chemical composition
of the local ISM. We provide a brief overview here (see, e.g., P. A. Crowther 2007,
for a more thorough review). WR stars are massive stars that have entered the core
He-burning phase and have lost their outer envelope either via strong stellar winds
or due to binarity effects (i.e., stripping via Roche Lobe overflow or mergers).
The first phase of WR stars occurs when the outer H layer has been ejected, revealing
the H core-burning products such that their spectra are characteristically He and
N rich but are H-poor. Such stars are known as nitrogen-type WR, or WN, stars, and
are often identified by strong N iii, N iv, and N v emission lines, especially the
broad optical “blue bump” near λ4650. The blue bump is a complex of features, including
N iii λλ4634,4642, C iii λ4649,4667, Fe iii λ4660, and He ii λ4687. Subsequently,
stars that are massive enough for core He-burning and for their winds to remove
their outer He envelope and expose the produced C enter the WR carbon (WC) phase.
WC stars also have strong, broad He ii emission and strong C and O emission, such
that they are identified by the optical WR C iv λλ5803,5814 doublet (the “red bump”).
As a result, the typically very strong winds of the WR phase can produce significant
N enrichment during the WN phase and drive strong C ejection during the WC phase.
After the WC phase, a WR-oxygen phase may ensue, but we forgo discussion of this
phase here.\r\n\r\nThe rest-frame UV and optical spectra shown in Figure 2 can be
used to characterize the WR nature of the stellar population in RXCJ2248-ID3. Both
the UV and optical He ii emission features are kinematically broadened compared
to the narrow nebular emission features in RXCJ2248-ID3, indicative of WR or VMS
winds. F. Martins et al. (2023, 2025) have shown that young star-forming regions
dominated by VMSs can be distinguished from WR stars using the morphology of the
blue and red bumps. In particular, VMSs produce blue bumps with He ii λ4687 emission
but little to no N iii emission and red bumps with narrow C iv λλ5803,5814 emission.
Thus, strong detections of N iii in the blue bump favor a WN interpretation (e.g.,
F. Martins et al. 2023; D. A. Berg et al. 2024; T. E. Rivera-Thorsen et al. 2024).\r\n\r\nThe
upper right-hand panel of Figure 2 highlights the blue bump spectral regime, showing
weak, broad He ii and N iii λ4642 in RXCJ2248-ID3, both of which are characteristic
of metal-poor WN stars. Just redward of the N iii λ4642 line in the blue bump (but
blueward of [Fe iii]), a second less prominent emission feature is seen, but it
is difficult to determine whether this is due to C iii or O ii emission, or both.
Furthermore, the red C iv bump is not detected, suggesting little to no contributions
from WC stars or VMSs in the spectrum. Thus, we only significantly detect the blue
WR bump, suggesting that WN stars are likely present.\r\n\r\n4. Nebular Properties\r\nUsing
the updated narrow-component emission-line fits presented in Section 2.2, we determined
the nebular properties of RXCJ2248-ID3. Following D. A. Berg et al. (2021), we adopt
the four-zone ionization model to account for the high-ionization emission observed.
In this model, the ionization potential energy ranges of N+, S+2, O+2, and He+2
define the low-, intermediate-, high-, and very high-ionization zones, respectively.
For all calculations, we use the PyNeb package in Python with the atomic data adopted
in D. A. Berg et al. (2019), which includes a six-level atom model for oxygen in
order to utilize the UV O iii] λ1666 line. Below, we determine temperatures and
densities, although Te(O+2) and ne(N+3) were codetermined during the iterative reddening
calculation (see Section 2.3) in Section 4.1, ionization parameters in Section 4.2,
and abundances in Section 4.3.\r\n\r\nWe note that the UV spectra do not have sufficient
S/N to decompose narrow and broad components following the same method as the optical
lines. As a result, density diagnostics and abundances determined from UV lines
may include contributions from multiple kinematic components, while optical temperatures,
densities, and abundances are derived from narrow components alone. If the broad
component arises from gas with distinct physical conditions, this could introduce
systematic offsets. For this reason, we examine the potential impact of UV broad
components in Section 4.4.\r\n\r\n4.1. Temperature and Density\r\nOne of the unique
characteristics of RXCJ2248-ID3 is its large number of density-sensitive emission-line
ratios. M. W. Topping et al. (2024) previously reported densities from the three
UV line ratios of Si iii] λ1883/λ1892, characterizing the intermediate-ionization
zone, C iii] λ1907/λ1909, characterizing the intermediate- to high-ionization zone,
and N iv] λ1483/λ1486, characterizing the high- to very high-ionization zone. The
new high-S/N optical spectra enables us to measure, for the first time, densities
from the low-ionization [S ii] λ6717/6731 ratio and the high- to very high-ionization
[Ar iv] λ4713/λ4741 ratio.\r\n\r\nWe use our narrow-component dereddened flux measurements
to compute densities for all five line ratios and the high-ionization zone temperature
from the [O iii] λ4364/λ5008 ratio. The high-ionization zones Te(O+2) and ne(N+3)
were simultaneously determined during the iterative reddening calculation in Section
2.3 to account for the sensitivities of both diagnostics. If the low density limit
was assumed instead (ne ≲ 102 cm−3), as is common practice at low-redshift, the
observed [O iii] λ4364/λ5008 flux ratio would lead to unphysical temperatures (i.e.,
above the limit set by H cooling of ∼2.5 × 104 K). Thus, a physical and robust solution
requires high densities to properly account for the reduced λ5008 flux due to collisional
de-excitation. Furthermore, Z. Martinez et al. (2025) recently showed that densities
derived from both optical and UV diagnostics underpredict the true volume-averaged
density in multiphase, high-density systems, with more severe underprediction from
the optical diagnostics. Therefore, it is necessary to use UV density diagnostics
in high-density environments, though the true density will still be underestimated
in multiphase gas (see, e.g., Figure 11 of Z. Martinez et al. 2025).\r\n\r\nFor
the high-ionization zone, we found a Te(O+2) = 1.97 ±0.03 × 104 K and ne(N+3) cm−3,
which is consistent with the density of ne(N+3) cm−3 reported by M. W. Topping et
al. (2024), but lower than their temperature of 2.46 ± 0.26 × 104 K due to our broad
component fits of both [O iii] λ4364 and λ5008. Adopting our Te(O+2) as the high-ionization
temperature (Te,high), we then applied the Te–Te relations of D. R. Garnett (1992)
to estimate the intermediate-ionization temperature (Te,int.) and low-ionization
temperature (Te,low).\r\n\r\nThe determined temperatures were used for the subsequent
density calculations in their respective ionization zones. Note that the [Ar iv]
λ4713 and He i λ4714 lines are blended in the G395M grating. Therefore, we corrected
the [Ar iv] λ4713 flux for the He i λ4714 contribution, predicting the He i λ4714
flux from the measured He i λ4473 flux and the theoretical He i λ4714/λ4473 ratio
(∼0.21 for the conditions in RXCJ2248-ID). The resulting densities, all of which
fall within their respective diagnostic ranges, and temperatures are reported in
Table 2.\r\n\r\nRemarkably, RXCJ2248-ID3 is one of few galaxies, and the only galaxy
yet at high redshifts, to have significant (>3σ) electron density measurements from
five different ions that span a large ionization range (∼10–77 eV). Furthermore,
the densities in RXCJ2248-ID3 appear to be organized into an interesting nebular
stratification. The UV emission lines trace the densest gas, with ne(N+3) = 2.65
× 105 cm−3 in the highest-ionization gas, followed by ne(C+2) = 7.94 × 104 cm−3
and ne(Si+2) = 4.77 × 104 cm−3. In contrast, the optical high-ionization lines are
emitted from regions of lower densities: the optical [Ar iv] diagnostic has an overlapping
ionization energy range with the UV N iv] diagnostic but a density that is an order
of magnitude lower.\r\n\r\nThere are two possible interpretations of the measured
array of densities. First, since the UV lines also have higher excitation energies,
they could originate preferentially from hotter, denser clumps. This would imply
a strongly inhomogeneous ISM, in which compact, high-pressure structures dominate
the UV line emission while somewhat more diffuse gas produces much of the optical
emission. Alternatively, the multiphase ISM may span a smaller dynamic range of
densities than we measure due to the suppression of the optical diagnostics. Z.
Martinez et al. (2025) showed that for an ISM with a mix of low- (e.g., 103 cm−3)
and high-density gas (e.g., 105 cm−3) that has a true volumetric density that is
somewhere in between, the low-ionization optical diagnostics will always be significantly
biased low, close to the low-density gas value, until the fraction of high-density
gas is very high (e.g., >95%). This effect occurs when ne-diagnostic line ratios
have low critical densities (e.g., ne,crit([S ii])≈2 × 103–5 × 103 cm−3), such that
emission from the high-density gas is collisionally suppressed beyond detection.
The magnitude of this effect decreases with increasing critical density such that
[S ii] is significantly affected, [Ar iv] is moderately affected (ne,crit ≈ 2 ×
104–2 × 105 cm−3), and the UV Si iii], C iii], and N iv] (ne,crit ≈ 5 × 104–5 ×
1010 cm−3) are minimally affected, albeit still biased low. In this scenario, there
would still be density stratification, but with smaller differences.\r\n\r\nAll
together, the nebular diagnostics in RXCJ2248-ID3 support a picture of a multiphase
nebula with density and temperature stratification, likely reflecting a clumpy ISM
shaped by the feedback and local radiation field variations of bursty star formation
(see, also, N. Choustikov et al. 2025; Y. Harikane et al. 2025b; M. Usui et al.
2025). This picture is also consistent with the density stratification that has
been reported for dwarf galaxies both near and far (e.g., B. L. James et al. 2016;
D. A. Berg et al. 2021; M. Mingozzi et al. 2022; X. Ji et al. 2024; M. W. Topping
et al. 2024), but with typical densities increasing with redshift (e.g., Y. Isobe
et al. 2023; Abdurro’uf et al. 2024; Z. Martinez et al. 2025; M. W. Topping et al.
2025a).\r\n\r\n4.2. Ionization Parameter\r\nThe ionization parameter of RXCJ2248-ID3,
, determined using the typical O32 = Iλ5008/Iλ3728 diagnostic is reported in M.
W. Topping et al. (2024) to be in the high range of to −1. We recompute the ionization
parameter for RXCJ2248-ID3 using the O32 and N43 = Iλλ1483,1486/Iλ1750 diagnostics
from Z. Martinez et al. (2025) that are calibrated for densities in the 102 ≤ ne(cm−3)
≤ 106 range. We estimate a using O32, which is consistent with the value reported
by M. W. Topping et al. (2024), and using N43. Note, however, that the O32 diagnostic
is very sensitive to the assumed density (Z. Martinez et al. 2025), making this
value highly uncertain in dense gas. For example, densities of ne = 103–105 cm−3
would lead to a range of to −2.04, respectively.\r\n\r\n4.3. Abundances\r\nHere,
we present direct-method abundances of oxygen-to-hydrogen (O/H) (Section 4.3.1),
N/O (Section 4.3.2), carbon-to-oxygen (C/O) (Section 4.3.3), and silicon-to-oxygen
(Si/O) (Section 4.3.4) for RXCJ2248-ID3 using narrow-line flux ratios and the measured
temperatures and densities presented in Section 4.1. Nearly all of the optical lines
used in this work have sufficient S/N to simultaneously constrain broad and narrow
emission components, but there are a few exceptions, all of which are low-ionization
lines. The [O ii] λ3728 line was not covered by the GLIMPSE-D spectrum and so lacks
the S/N to fit broad components. Both [N ii] λ6585 and [S ii] λλ6718,6733 are covered
in the high-S/N GLIMPSE-D spectrum but are either blended with stronger features
or too weak to fit broad components. On the other hand, the [O ii] and [S ii] lines
have low critical densities around ne,crit ∼ 103 cm−3 such that any moderate to
high-density broad components are likely collisionally de-excited away. Their narrow-component
fluxes could also be significantly reduced by collisional de-excitation; however,
the missing [O ii] emission is likely small in the absolute sense for such a high-ionization
object. Emission from [N ii] is less likely to be collisionally de-excited (ne,crit
∼ 105 cm−3), so a hidden broad component could lead to an overestimate of the N/O
abundance, but this effect would be somewhat countered by the underestimated [O
ii] flux. In the end, the consistency of N/O derived independently from UV and optical
tracers in Section 4.3.2 below suggests that these effects do not significantly
impact our results.\r\n\r\nTo calculate the total or relative abundance of an element,
we determine and sum the individual observed ions and then apply an ionization correction
factor to account for unseen prominent ionization states. The abundance of an individual
ionic species, Xi, relative to hydrogen is determined as\r\n\r\nwhere jλ(i) is the
emissivity determined for the appropriate ionization zone temperature and density.
Given the tendency of the optical density diagnostics to severely underestimate
the density in high-density environments, we instead adopt the UV-derived densities.
Note that the abundances presented below have not been corrected for the fraction
of atoms embedded in dust. However, the level of depletion onto dust grains is expected
to be small for the low metallicity of RXCJ2248-ID3 (e.g., A. Rémy-Ruyer et al.
2014; F. Galliano et al. 2018; J. Roman-Duval et al. 2022). Y. Isobe et al. (2026)
also infer negligible dust depletion for RXCJ2248-ID3 based on the high value of
Si/O that that they determine, but this is inconsistent with the value we determine
below. Details of elemental abundance determinations are given below.\r\n\r\n4.3.1.
Oxygen Abundance\r\nWe determine the total O/H abundance as the sum of the O+/H+
and O+2/H+ ionic abundances, determined from the [O ii] λ3728 and [O iii] λλ4960,5008
optical emission lines. We observe no strong O0 or O+3 emission, indicating that
contributions from other ions are negligible. The resulting ionic and total oxygen
abundances are presented in Table 2. Similar to M. J. Hayes et al. (2025) and Z.
Martinez et al. (2025), we find that one of the most significant effects of accounting
for high densities is the resulting decrease in electron temperature and subsequent
increase in oxygen abundance (see, also, H. Katz et al. 2023). In our work, this
results both from accounting for the missing [O iii] λ5008 flux due to collisional
de-excitation and from correcting the narrow emission for broad emission components
at their base. M. W. Topping et al. (2024) also incorporated the high densities
seen in RXCJ2248-ID3 but did not have the S/N to fit the broad emission components
in both [O iii] λ5008 and λ4364. As a result, we measure an oxygen abundance of
. Note that if unresolved high-density clumps (ne ≳ 105 cm−3) are present (as suggested
in, e.g., Section 2.3), it could introduce additional uncertainty by biasing the
luminosity-weighted [O iii] λ4364/λ5008 ratio to higher densities, which would drive
the derived Te higher and O/H abundance lower. However, Z. Martinez et al. (2025,
see Figure 11), showed that the use of high-critical density UV density diagnostics
largely mitigate this effect in a density stratified medium.\r\n\r\n4.3.2. Relative
N/O Abundance\r\nThe extraordinary simultaneous detections of [N ii] λ6585, N iii]
λ1750, and N iv] λλ1483,1487 enable multiple determinations of the N/O abundance.
Therefore, we calculate N/O abundances using four different ionic methods\r\n\r\n\r\n\r\n\r\nwhere
[O ii] λ3728 is used for the N+/O+ determination, O iii] λ1666 is used for the N+2/O+2
and N+3/O+2 calculations, and X(N+i) and X(O+i) are the N and O ionization fractions,
respectively. We use the density-dependent ICFs from Z. Martinez et al. (2025),
who provide prescriptions for densities of ne = 102, 103, 104, 105, and 106 cm−3.
We, therefore, round our density measurements to the nearest order of magnitude
and use the intermediate-ionization for the N+/O+ ICF and the high-ionization for
the N+2/O+2 and N+3/O+2 ICFs. The resulting N ICFs and N/O abundances are reported
in Table 3.\r\n\r\nThe four N/O determinations of RXCJ2248-ID3 are in close agreement,
far above the expected value for its metallicity. Visually, this is shown in the
upper left-hand panel of Figure 4, which plots the relative N/O versus O/H abundance
with RXCJ2248-ID3 marked by purple diamonds. The traditional N/O–O/H trend has been
established by many z ∼ 0 studies of H ii regions and galaxies (gray points: C.
Esteban et al. 2002, 2009, 2014; L. S. Pilyugin & T. X. Thuan 2005; L. van Zee &
M. Haynes 2006; J. García-Rojas & C. Esteban 2007; Á. R. López-Sánchez et al. 2007;
D. A. Berg et al. 2012, 2016,2019, 2020). The empirical trend is a bimodal relationship,
with a flat trend due to primary (or metallicity-independent) N production at low
metallicities () and an increasing N/O trend with O/H as secondary (or metallicity-dependent)
N production becomes increasingly important at higher metallicities (). As a visual
guide, the primary N/O plateau from D. A. Berg et al. (2019, dashed purple line)
is shown and the empirical stellar curve from D. C. Nicholls et al. (2017, solid
green line) is shown as an example of the full primary and secondary curve.\r\n\r\nZoom
InZoom OutReset image size\r\nFigure 4. Relative C and N abundance trends versus
metallicity. Nitrogen to oxygen ratio versus oxygen abundance for star-forming galaxies
is plotted in the left panels, while C/O ratio versus oxygen abundance is plotted
in the middle panels, and carbon to nitrogen abundance versus oxygen abundance is
plotted in the right panels. Top row: RXCJ2248-ID3 is shown relative to the observed
z ∼ 0 trend and other high-z galaxies. The abundances for RXCJ2248-ID3 are shown
as purple diamonds, where multiple N/O points show the measurements for each ionic
N/O calculation method. For comparison, we also plot the abundances derived for
RXCJ2248-ID3 by M. W. Topping et al. (2024) as turquoise squares. The typical bimodal
N/O trend is characterized by local dwarf (gray diamonds; L. van Zee & M. Haynes
2006; D. A. Berg et al. 2012, 2016, 2019) and spiral galaxy (gray circles; C. Esteban
et al. 2002, 2009, 2014; L. S. Pilyugin & T. X. Thuan 2005; J. García-Rojas & C.
Esteban 2007; Á. R. López-Sánchez et al. 2007; D. A. Berg et al. 2020) H ii region
measurements. The primary N/O plateau from D. A. Berg et al. (2019) is shown as
a dashed purple line, while the solid green line is the empirical stellar curve
from D. C. Nicholls et al. (2017). Additional C/O literature measurements for dwarf
galaxies are from M. A. Peña-Guerrero et al. (2017) and P. Senchyna et al. (2017).
Abundances for z > 2 galaxies from Z. Martinez et al. (2025) are plotted as blue
plus signs for galaxies with UV N+2/O+2 derived abundances and pentagons for optical
N+/O+ derived abundances. Bottom row: The same observed samples are shown as the
top row, but with the z ∼ 0 sample represented by the shaded gray regions. The observed
abundances of RXCJ2248-ID3 are compared to updated dual-burst chemical evolution
models of C. Kobayashi & A. Ferrara (2024, string of circles), color coded by age
since onset of the second burst. The models have been modified to reproduce both
the enhanced N/O and relatively deficient C/O observed for RXCJ2248-ID3, which requires
enrichment from WN but very little WC enrichment, as expected at low metallicities.\r\n\r\nDownload
figure:\r\n\r\nStandard imageHigh-resolution image\r\nFor comparison, we plot the
high-quality high-redshift N/O measurements that were calculated in a consistent
manner as the present work (with direct-method Te and ne determinations and ne-dependent
ICFs) by Z. Martinez et al. (2025). N/O abundances determined using N+2/O+2 are
plotted as blue + symbols, while N+/O+ determinations are plotted as blue pentagons.
Of these galaxies, the closest comparison to RXCJ2248-ID3 is CEERS-1019 (see, also,
R. Marques-Chaves et al. 2024), while only GDS 3073 and GN-z11 have higher relative
N/O abundances and only GDS 3073 is more enhanced in N/O for its O/H abundance.\r\n\r\nWe
find that all four ionic methods produce consistently high N/O values within their
uncertainties, with a weighted mean of . This is an important result because RXCJ2248-ID3
is the first galaxy to have consistently enhanced N/O abundances measured from both
the rest-frame UV high-ionization and the optical low-ionization emission lines.
Furthermore, measuring consistent N/O values from three different ionic methods
strengthens our confidence in the robustness of the N/O measurement, although uniform
N/O across the ionization structure of the nebula is not a given in a stratified
medium. While there is strong evidence for a stratified, or perhaps very clumpy,
density structure in RXCJ2248-ID, the N/O abundance appears to be well mixed.\r\n\r\n4.3.3.
Relative C/O Abundance\r\nMeasuring the C/O abundance provides a crucial comparative
baseline for interpreting the origin of elevated N/O in RXCJ2248-ID3. Similar to
N, C has a pseudosecondary17 production pathway, but the dominant nucleosynthetic
sources and timescales differ for C and N. Briefly, both C and O are primarily produced
in massive stars (>8 M⊙) on relatively short timescales such that the C/O ratio
is a relatively stable tracer of massive star yields, although some C is produced
via low- to intermediate-mass AGB stars (∼1.5–3 M⊙). In contrast, some N is produced
by massive stars (e.g., through rotational mixing and WR winds) but most N comes
from intermediate-mass AGB stars (∼4–8 M⊙), which release N on longer timescales
(∼200 Myr). Therefore, N/O and C/O together serve as diagnostics of the recent star
formation history, constraining the recent enrichment mechanisms of galaxies (e.g.,
D. R. Garnett 1990; R. B. C. Henry et al. 2000; C. Chiappini et al. 2003; E. Pérez-Montero
& T. Contini 2009; D. A. Berg et al. 2019; E. Pérez-Montero et al. 2021).\r\n\r\nRelative
C/O abundances are typically determined using the C iii] λλ1907,1909/O iii] λ1666
ratio to calculate C+2/O+2 and assuming that C/O ≈ C+2/O+2. This method is sometimes
used alone owing to the fact that (1) C+2 and O+2 have somewhat similar ionization
potentials (24.38 and 35.12 eV, respectively), (2) the upper levels of the λ1666
and λλ1907,1909 transitions have similar excitation potentials (∼6.5 and ∼7.5 eV,
respectively), and (3) the integrated fluxes of λ1666 and λλ1907,1909 are not sensitive
to collisional de-excitation for the densities measured here. However, for the high-ionization
nebulae in RXCJ2248-ID3, it is important to account for contributions from the C+3
species and any unseen species. We note that the C iv λλ1548,1550 doublet is clearly
observed in the rest-UV spectrum of RXCJ2248-ID3, but these lines are resonant and
can be affected by the C iv stellar wind feature and ISM absorption, and so determining
the intrinsic flux and subsequent C+3 abundance is challenging. Instead, we use
an ICF determined from the photoionization models presented in Z. Martinez et al.
(2025) such that\r\n\r\nWe used the and a density of ne(C+2) ∼ 105 cm−3 to determine
the C ICF. The resulting C ICF and C/O abundance are reported in Table 3.\r\n\r\nThe
C/O and C/N abundances for RXCJ2248-ID3 are plotted in the upper middle and right-hand
panels of Figure 4. Empirical trends of C/N at z ∼ 0 are found to be flat, albeit
with significant scatter (see shading in Figure 4), suggesting that the dominant
nucleosynthetic mechanisms of C are similar to those of N (e.g., D. R. Garnett et
al. 1999; C. Esteban et al. 2014; D. A. Berg et al. 2016, 2019). However, while
the production of both C and N appear to be metallicity-dependent, the scatter in
their trend is consistent with differing production timescales due to stars of different
masses. Thus, the variations observed in CNO abundance patterns of high-redshift
galaxies may be the result of taking a snapshot of many galaxies at different times
since their most recent onset of star formation.\r\n\r\nRXCJ2248-ID3 appears to
have a similar CNO abundance pattern to other high-redshift N emitters, characterized
by enhanced N/O but relatively deficient C/O such that their C/N is very deficient
compared to the expectations from low-redshift trends. This suggests that these
high-redshift N-emitting galaxies are enhanced in N relative to both O and C. If
massive stars in the WN phase are present, they will have recently produced 14N
at the expense of 12C through the CNO cycle, meaning C used as a catalyst in the
cycle initiation will have been consumed as N is removed during the bottleneck step
via dredged up, preventing the return of C at cycle completion. Thus, C/N-deficiency
is consistent with a recent, intense episode of N enrichment and C consumption from
WN stars. Conversely, if both N/O and C/O were elevated in tandem, it could point
to broader enrichment by massive stars, such as enrichment from both WN and WC stars,
whose contributions increase at higher metallicities.\r\n\r\n4.3.4. Relative Si/O
Abundance\r\nDetecting Si iii] λλ1883,1892 in RXCJ2248-ID3 enables the rare opportunity
to measure the silicon-to-oxygen (Si/O) abundance in a z > 5 galaxy (see, also,
Y. Isobe et al. 2026, for Si/O in GN-z11). Silicon abundances are important for
multiple reasons. Silicon is highly refractory, making the Si/O ratio a sensitive
probe of dust depletion. Additionally, Si probes different channels of chemical
enrichment than CNO elements, as it is primarily an α-element produced by CCSNe,
but Type Ia SNe, AGB stars, and even pair-instability SNe are all expected to contribute
to the total Si abundance. For RXCJ2248-ID3 we determine the Si/O abundance using
the observed Si iii] λλ1883,1892/O iii] λ1666 ratio to calculate Si+2/O+2. Because
Si+2 and O+2 have rather different ionization potentials (16.3 eV versus 35.1 eV,
respectively), a Si ICF is required to convert Si+2/O+2 to total Si/O via\r\n\r\nSi
ICFs have been reported previously (e.g., D. R. Garnett et al. 1995), but none account
for the high-density conditions observed in RXCJ2248-ID3. Therefore, we determined
a Si ICF = 3.507 using the photoionization models presented in Z. Martinez et al.
(2025) using the and a density of ne(Si+2) ∼ 104 cm−3. Reported in Table 3, the
resulting (Si/O) = −1.781 ± 0.157 abundance is typical of metal-poor dwarf galaxies
(e.g., D. R. Garnett et al. 1995; Y. I. Izotov & T. X. Thuan 1999), consistent with
normal massive star production and low dust depletion.\r\n\r\n4.4. Potential Impact
of UV Broad Components\r\nThe exceptionally high S/N of the rest-optical GLIMPSE-D
spectrum allows for broad emission component fits that the rest-UV spectrum does
not. In Section 2.2, we found the broad emission component contribution to the narrow
[O iii] λ5008 flux to be 10.8%. To examine the possible effects such contamination
has on calculations of nebular conditions and abundances, we adopt 10.8% as the
contamination upper limit to the UV emission lines. We first consider the impact
on the UV density determinations, where we allow the broad components of the UV
density-sensitive emission-line ratios to have densities ranging from 102–106 cm−3.
After subtracting the potential broad component contribution, the revised densities
change up to Δne(Si+2), Δne(C+2), and Δne(N+3) over the range of broad component
densities considered. These values are within the reported uncertainties in Table
3, with the exception of the ∼1.2σ deviation for Δne of C+2.\r\n\r\nNext, we tested
the subsequent impact of UV densities that have been revised for possible broad
components on the properties determined from rest-optical emission lines: Te(O+2),
O/H, and N/O. For the range of Δne(N+3) above, the resulting K, which is within
1σ–2σ of the reported value in Table 3. Similarly, the impact of the revised densities
and temperatures on the oxygen abundance, dex, is also within 1σ–2σ. The impact
is even smaller for the nitrogen abundance, with dex being much smaller than the
N/O uncertainty.\r\n\r\nRelative UV abundances are impacted by changes in both the
nebular conditions and the relevant abundance emission-line ratio. However, the
resulting abundance deviations are small and within the original uncertainties:
dex, dex, and dex. Thus, we conclude that while considering the impacts of hidden
broad component contributions to the measured UV fluxes is important, the potential
biases do not affect the main results or conclusions of this work.\r\n\r\n5. A Short
Window of Intense WR Nitrogen Enrichment\r\nWe have presented evidence for WN stars
in RXCJ2248-ID3 in two forms: first, the rest-frame optical WR blue bump discussed
in Section 3 and shown in Figure 2; and second, a qualitative comparison of the
CNO abundances to patterns expected for WR stars in Section 4.3 and Figure 4. Below,
we examine the plausibility and impact of these WN stars by comparing RXCJ2248-ID3
to expected trends for WR stars with metallicity (Section 5.1), testing whether
stellar yields can reproduce the observed CNO abundance pattern (Section 5.2) and
assessing whether RXCJ2248-ID3’s stellar population can produce its inferred mass
of ionized N (Section 5.3). Together, these lines of investigation suggest that
the enhanced N/O and suppressed C/O in RXCJ2248-ID3 represent a short-lived enrichment
phase, unique to metal-poor, highly star-forming galaxies in the early Universe
(Section 5.4).\r\n\r\n5.1. WN Stars: The Dominant WR Phase at Low Metallicity\r\nTo
date, no individual resolved WR stars have been directly observed at metallicities
as low as RXCJ2248-ID3 (Z ∼ 0.1Z⊙). This is due, in part, to the lack of sufficiently
close (D ≲ 1 Mpc for the young, crowded clusters hosting WR stars), metal-poor,
star-forming galaxies (see C. Kehrig et al. 2013 for the closest metal-poor WR galaxy),
but a scarcity of WR stars in metal-poor environments is also expected because mass
loss through stellar winds scales with metallicity. We show the trend of the number
of WC/WN stars as a function of metallicity in Figure 5. The observed number of
WC/WN stars in M31 (∼175% Z⊙), the Milky Way (MW; Z⊙), M33 (∼40%–110% Z⊙), the Large
Magellanic Cloud (LMC; ∼40% Z⊙), and the Small Magellanic Cloud (SMC; ∼20% Z⊙) suggest
that the number of the WN/WC number ratio increases with decreasing metallicity
(e.g., G. Meynet & A. Maeder 2005; P. A. Crowther 2007; P. Massey et al. 2015; K.
Neugent & P. Massey 2019). This is because weaker metal line-driven winds, rotation,
or binary effects in metal-poor stars may be able to expose their nitrogen-rich
layers and initiate the WN phase but be insufficient to strip the stellar He atmosphere
and reveal the carbon-rich core to initiate the WC phase. Thus, if WR stars form
at Z ∼ 10% Z⊙, they are expected to be overwhelmingly WN-type. Additionally, A.
A. C. Sander et al. (2026) recently discovered a new class of WN–WO stars that point
to a low-metallicity WR evolutionary channel in which stars pass directly from the
WN to WO phase, potentially explaining spectra that show evidence for WN-like enrichment
and hard ionizing radiation without clear WC signatures.\r\n\r\nZoom InZoom OutReset
image size\r\nFigure 5. Observed and theoretical ratios of WC/WN star numbers as
a function of metallicity. Observed values for the SMC, LMC, MW, and M31 were compiled
by K. Neugent & P. Massey (2019), while newer values for M33 come from K. F. Neugent
& P. Massey (2023). For comparison, we also plot the trend presented in P. Massey
et al. (2017) for BPASS v2.0 binary stellar population synthesis burst models for
12+log(O/H) > 8 (solid line green line), which we extrapolate to lower metallicities
(dashed line). Enrichment from WR stars was used to explain the CNO abundances in
GN-z11 by C. Kobayashi & A. Ferrara (2024). We note the metallicity for GN-z11 determined
by Z. Martinez et al. (2025) is consistent with a WC/WN ratio of ∼0.1–0.2 and the
metallicity for RXCJ2248-ID3 from the current work, which predicts a much lower
WC/WN ratio of ∼0.03–0.10. Therefore, very little carbon enrichment from WC stars
is expected for RXCJ2248-ID3.\r\n\r\nDownload figure:\r\n\r\nStandard imageHigh-resolution
image\r\nThe spectral features of RXCJ2248-ID3 support the picture of WN star feedback
at low metallicity. As shown in Figure 2, the He ii emission is moderately broadened,
the N iii λ4642 line in the blue bump is prominent, and there is no evidence for
the red bump C iv feature, all consistent with the presence of WN stars at low metallicity.
The weakness of the He ii emission in terms of both flux and velocity width is expected
for the low-metallicity environment of RXCJ2248-ID3 (∼10% Z⊙) due to reduced wind
velocities and mass-loss rates (e.g., A. A. C. Sander et al. 2020). Similarly weak
WN features have also been reported in the nearby metal-poor galaxy SBS 0335-052
(Y. I. Izotov et al. 2006) and, at cosmic noon, the z ∼ 2.37 lensed galaxy the Sunburst
Arc (T. E. Rivera-Thorsen et al. 2024) and the z ∼ 2.22 M4327 galaxy (M. Curti et
al. 2025b).\r\n\r\nWe plot the WR blue bump profile of RXCJ2248-ID3 relative to
the Sunburst Arc and M4327 in Figure 6. For ease of comparison, we convolve the
Sunburst Arc R ∼ 2700 JWST/NIRSpec G140H spectrum to the R ∼ 1000 resolution of
the RXCJ2248-ID3 spectrum. For M4327, we retrieved the G140M spectrum obtained as
part of the Measuring Abundance at High Redshift with the Te Approach Survey (MARTA;
E. Cataldi et al. 2025) from the Dawn JWST Archive (DJA; K. E. Heintz et al. 2024;
A. de Graaff et al. 2025). Both the Sunburst Arc and M4327 spectra were scaled to
similar He ii strengths as RXCJ2248-ID3. These spectra immediately reveal similar
profiles, but with three distinct differences: (1) RXCJ2248-ID3 exhibits higher
gas ionization, as evidenced by the strong [Ar iv] λλ4713,4741 emission; (2) the
He ii stellar wind feature is significantly broader in both the Sunburst Arc (FWHM
= 1370 km s−1) and M4327 (FWHM = 1460 km s−1) than RXCJ2248-ID3 (FWHM = 530 km s−1),
consistent with stronger stellar winds at the higher metallicities of the Sunburst
Arc: (or Z ∼ 0.7 Z⊙; Z. Martinez et al. 2025) and M4327: (or Z ∼ 0.3 Z⊙; M. Curti
et al. 2025b); and (3) the WR N iii λ4642 line is much stronger in RXCJ2248-ID3,
which lacks WR C iv λλ5803,5814 emission, while the Sunburst Arc and M4327 exhibit
both N iii and C iv emission. These differences support a scenario in which the
z ∼ 2 WR galaxies hosts both WC and WN stars, but the more metal-poor RXCJ2248-ID3
hosts a young population of WN stars with no or very little WC contribution.\r\n\r\nZoom
InZoom OutReset image size\r\nFigure 6. The blue WR region of the optical spectrum
of RXCJ2248-ID3 (purple) is shown in comparison to the z ∼ 2.37 Sunburst Arc spectrum
from T. E. Rivera-Thorsen et al. (2024, blue), which has been convolved to R ∼ 1000
to match RXCJ2248-ID3, and the z = 2.22 M4327 spectrum obtained from the DJA, but
originally presented in M. Curti et al. (2025b, turquoise). All three galaxies show
characteristic signs of hosting WN stars but RXCJ2248-ID3 shows striking N iii λ4642
emission that is much stronger than both the Sunburst Arc and M4327. On the other
hand, the Sunburst Arc and M4327 show broader He ii emission, which is expected
for more metal-rich galaxies as stellar winds scale with metallicity.\r\n\r\nDownload
figure:\r\n\r\nStandard imageHigh-resolution image\r\n5.2. Relative Chemical Enrichment
from WN Stars\r\nWith the highest redshift detection of WN stars to date, we now
explore their chemical yields as a source of the abundance pattern in RXCJ2248-ID3.
C. Charbonnel et al. (2023) performed a comparable analysis for the extreme N/O
ratio observed in GN-z11 and found that such rapid nitrogen enrichment could arise
from normal massive stars with M⋆ ∼ 20–120 M⊙ or from supermassive stars (M⋆ ≳ 1000
M⊙) in protoglobular cluster environments. Their results and those of R. Marques-Chaves
et al. (2024) further demonstrated that the short-lived WN-like phase can produce
large N/O ratios within a few megayears of the burst, consistent with the timescales
inferred here, but that the observed C/O ratios are only compatible over a very
short time interval. Building on this theoretical groundwork, C. Kobayashi & A.
Ferrara (2024) showed that a dual-burst chemical evolution model with a short WR-dominated
enrichment phase could also match GN-z11’s enrichment pattern. Similarly, R. Marques-Chaves
et al. (2024) used N yields from rotating massive stars to demonstrate that a young,
WR-dominated stellar population could reproduce the observed CNO enrichment pattern
in CEERS-1019.\r\n\r\nThe models above provide a valuable physical framework for
linking stellar yields to galaxy-scale abundance evolution at early times. To extend
the methodologies outlined by these works to RXCJ2248-ID3, we first examine the
dual-burst chemical evolution model of C. Kobayashi & A. Ferrara (2024), which was
fine-tuned to reproduce the enhanced N/O in GN-z11 (reported by R. Maiolino et al.
2024). This model invokes two bursts of star formation, where the second triggers
a narrow (≲1 Myr) phase of WR-dominated enrichment. While the model can easily reach
the N/O enrichment level of RXCJ2248-ID3, it was also designed to yield the higher
O/H and C/O abundances observed in GN-z11 than in RXCJ2248-ID3, which was achieved,
in part, by enrichment from WC stars. The updated O/H abundance for GN-z11 determined
by Z. Martinez et al. (2025) makes it consistent with some carbon enrichment from
WC stars, as shown in Figure 5. However, with a metallicity of only Z ∼ 0.10 Z⊙,
the WR population in RXCJ2248-ID3 is expected to consist of few WC stars, and so
an updated chemical evolution model is needed to match its unique CNO abundance
pattern.\r\n\r\nWe modify the C. Kobayashi & A. Ferrara (2024) dual-burst model
to be more appropriate for the metal-poor conditions in RXCJ2248-ID3. In particular,
the galactic chemical evolution (GCE) model uses the same star formation history
and the standard IMF (for 0.01–120 M⊙) as in the fiducial model in C. Kobayashi
& A. Ferrara (2024) but reduces the contribution from WC stars. C/O ratios of the
nucleosynthesis yields vary depending on the uncertain nuclear reaction rates (e.g.,
12C(α, γ)16O) and the treatment of convection and mass loss (C. Kobayashi et al.
2006). In the updated model, 12C and 16O yields are taken from C. Kobayashi et al.
(2020) for all mass ranges of stars but the contributions from the WC wind phase
is scaled to ∼15% in order to match the empirical trends and theoretical expectations
that most massive stars will have insufficient winds to remove their He envelopes
at such low metallicities.\r\n\r\nWe plot the updated metal-poor dual-burst model
in the bottom row of Figure 4 as a time-series of points that are color coded by
the age since the onset of the second burst. In this model, the observed N/O, O/H,
and C/O abundances of RXCJ2248-ID3 are reached simultaneously ∼4.2 Myr after the
onset of the second burst. This young age is consistent with enrichment from WN
stars and with the derived clump age of Myr (A. Claeyssens 2025). Thus, the N/O-enhanced
and relatively C/O-deficient conditions in RXCJ2248-ID3 are produced by a short-lived
evolutionary phase following intense, bursty star formation.\r\n\r\nWe note that
the duration and impact of the WN phase may be significantly extended if the stars
evolve in binary systems. In the M. Limongi & A. Chieffi (2018) single-star models,
the WN phase typically lasts ∼0.03–0.3 Myr and, due to the metallicity-dependent
winds, require high initial masses (∼40 M⊙) to expose the He- and N-rich layers.
However, in close binaries, envelope stripping via mass transfer or common-envelope
evolution can induce WR phases in lower-mass stars (20–30 M⊙), largely independent
of the stellar metallicity. This channel can significantly prolong the WN lifetime
(up to ∼1 Myr) depending on the binary mass ratio and separation (e.g., J. J. Eldridge
et al. 2017; Y. Götberg et al. 2019; D. R. Aguilera-Dena et al. 2022). As a result,
binary evolution may enhance both the frequency and duration of the chemically selective
N/O enrichment phase, such as that observed in RXCJ2248-ID. On the other hand, L.
Boco et al. (2025) successfully modeled observations of single WR stars in the SMC,
suggesting that binary stripping may not be required to produce WR stars at low
metallicity. Clearly, the frequency, lifetimes, and formation channels of WR stars
in low-metallicity environments are not yet well understood. Future work incorporating
current binary and single star WR pathways into chemical evolution models may, therefore,
be essential for capturing the full range of nitrogen feedback in low-metallicity
starbursts at high redshift.\r\n\r\nTaken together, the massive star enrichment
scenario presented here, and explored in C. Charbonnel et al. (2023), R. Marques-Chaves
et al. (2024), and C. Kobayashi & A. Ferrara (2024), demonstrates that selective
enrichment of nitrogen by WN-dominated feedback can naturally reproduce the observed
CNO abundance pattern in compact, low-metallicity starbursts such as RXCJ2248-ID3.
We can now paint a full picture of the ISM in RXCJ2248-ID3. The consistency of N/O
across ions spanning a wide range of ionization potentials suggests that the WN-enriched
material has been efficiently mixed throughout the ionized gas. This apparent chemical
homogeneity does not contradict the strong density and temperature stratification
inferred from our diagnostics: a clumpy or multiphase ISM can remain compositionally
uniform if the enriched ejecta are well dispersed. Given the extreme compactness
of RXCJ2248-ID3 (Re ≈ 20 pc), the characteristic dynamical and sound-crossing times
are only a few ×105 yr, comparable to or shorter than the duration of the WN phase
itself. Under such conditions, turbulent and radiative mixing can rapidly homogenize
the heavy-element yields, producing a chemically uniform yet physically structured
nebula.\r\n\r\n5.3. The N Mass Budget\r\nA crucial point of validation is whether
an intense burst of star formation so early in the Universe could have produced
the amount of N present in RXCJ2248-ID3. Similar to the analysis in R. Marques-Chaves
et al. (2024), we test this by first estimating the ionized nitrogen mass using\r\n\r\nwhere
the atomic mass ratio is mN/mH = 14 and N/H is the nitrogen abundance of the ionized
gas. The hydrogen gas mass MH is derived from the Hα luminosity as\r\n\r\nwhere
mH = 1.67 × 10−27 kg, h = 6.626 × 10−27 erg s−1, νHα is the frequency of the Hα
emission line, and cm3 s−1 is the Case B effective recombination coefficient for
Hα assuming a Te = 1.97 × 104 K. We estimate the Hα luminosity using a luminosity
distance of dL(z = 6.1025) =1.817 × 1029 cm, the collision-corrected narrow-component
Hα flux, and a magnification of μ = 6.8877 (L. Furtak et al. 2025) to be LHα = 1.20
× 1042 erg s−1. Combining this LHα with the equivalent width (EW)(Hα) = 1457 Å,
we derive the star formation rate (SFR) using the simulation-based SFR(Hα) calibration
from I. G. Kramarenko et al. (2026). This method was developed to be more appropriate
for the bursty conditions at high redshift than traditional calibrations and gives
SFR = 3.2 M⊙ yr−1, similar to the SED-derived SFRs assuming a constant SFH for 1
Myr () and 10 Myr (; see Table 1). Adopting a filling factor of ε = 0.01-0.10, assuming
a compact starburst (e.g., R. C. Kennicutt 1984; G. Stasińska & D. Schaerer 1997),
a density of 104 cm−3, and the measured N/H value, we calculate the ionized nitrogen
mass to be .\r\n\r\nWe then compute the total nitrogen mass that can be produced
by the recent burst of star formation using the integrated nitrogen yield produced
by the modified C. Kobayashi & A. Ferrara (2024) model for the SED-derived stellar
mass of assuming a continuous SFH over the duration of the second burst (∼4.2 Myr).
This results in a total N mass of 435 M⊙, implying that ∼% of the gas is retained
from the WN winds and ionized when matched to the expected ionized N mass (∼) from
the crudely calculated observed value. Thus, WN stars formed in a recent burst within
a compact, high-density, and very clumpy/inhomogeneous (low-filling-factor) environment
can plausibly explain the N mass in RXCJ2248-ID3, even at low metallicity (∼10%
Z⊙), without invoking a top-heavy IMF or exotic enrichment channels.\r\n\r\n5.4.
The Ephemeral Imprint of WN Star on High−z Galaxies\r\nThe prominence of N/O enhancement
at z ≳ 5 but relative rarity in local star-forming galaxies likely reflects a combination
of environmental conditions and evolutionary factors that are unique to the early
Universe. To examine the likely environments, we plot the SFR surface density (ΣSFR)
versus EW of Hβ in Figure 7 for both z ≳ 6 N emitters (RXCJ2248-ID3: M. W. Topping
et al. 2024, this work; GNz9p4: D. Schaerer et al. 2024; GN-z11, EW(Hβ) inferred
from Hγ: A. J. Bunker et al. 2023; S. Tacchella et al. 2023; GDS 3073: E. Vanzella
et al. 2010; H. Übler et al. 2023; X. Ji et al. 2024; CEERS-1019: R. L. Larson et
al. 2023; R. Marques-Chaves et al. 2024; A1703-zd6: M. W. Topping et al. 2025b)
and local star-forming galaxies with enhanced SFRs from the COS Legacy Archive Spectroscopic
SurveY (CLASSY; B. L. James et al. 2021; D. A. Berg et al. 2022; N/O from K. Z.
Arellano-Córdova et al. 2025). The high-redshift galaxies, such as RXCJ2248-ID3,
exhibit compact morphologies (Re ≲ 102 pc) that lead to much higher SFR surface
densities than seen at z ∼ 0, as well as bursty star formation histories that favor
the rapid buildup of massive stars capable of entering the short-lived WN phases
(M⋆ > 20 M⊙). The high-redshift N emitters also have high Hβ EWs (>200 Å) that are
indicative of young current bursts of star formation (<5 Myr). This suggests that
compactness alone is not enough to observe enhanced N/O; we must also observe these
galaxies at the fleeting moments of very young bursts when WR stars are most active.\r\n\r\nZoom
InZoom OutReset image size\r\nFigure 7. SFR surface density versus Hβ EW for high-redshift
(z > 5) N emitters versus z ∼ 0 galaxies from the CLASSY survey (SFR: D. A. Berg
et al. 2022; N/O: K. Z. Arellano-Córdova et al. 2025), which have enhanced SFRs
similar to z ∼ 2–3 galaxies. High-redshift N emitters are only observed at young
ages (≲5 Myr), as indicated by the high Hβ EWs (EW> 200 Å), and in compact, dense
environments (ΣSFR > 10 M⊙ yr−1 kpc−1). Note that RXCJ2248-ID3 is plotted here using
the properties derived from M. W. Topping et al. (2024) for continuous star formation
to be consistent with the other N-emitter measurements.\r\n\r\nDownload figure:\r\n\r\nStandard
imageHigh-resolution image\r\nFigure 7 suggests a scenario of elevated N/O at low
metallicity being preferentially seen in galaxies with high SFR surface densities
and young stellar ages (e.g., D. Schaerer et al. 2024; M. W. Topping et al. 2024;
Z. Martinez et al. 2025). R. Marques-Chaves et al. (2024) also suggest that the
elevated N/O and high-ionization spectrum of CEERS-1019 trace a short evolutionary
window of a ≲5 Myr burst dominated by WN-like feedback. Furthermore, the theoretical
models of C. Charbonnel et al. (2023) predict that such phases are characteristic
of young, dense stellar systems, potentially analogous to protoglobular clusters,
reinforcing that our observed WN-driven enrichment is a natural outcome of clustered,
bursty star formation at early times.\r\n\r\nAt low metallicity, weaker stellar
winds require higher initial masses for stars to reach the WR phase, so a larger
total stellar mass must form in a burst to produce a detectable population of WN
stars. In compact galaxies beyond cosmic noon, this condition is naturally met in
systems with high SFR surface densities, which statistically sample the upper IMF
more fully and produce a detectable population of WN stars (e.g., J. Brinchmann
et al. 2008; M. Shirazi & J. Brinchmann 2012). Furthermore, the WR enrichment signature
is short-lived: it must be captured during the brief WN-dominated phase (tburst
≲ 5 Myr and ΔtWN ≲ 0.3 Myr), before dilution from WC stars, CCSNe, or delayed AGB
enrichment. These timing constraints imply that only a small fraction of the star-forming
galaxies in the distant Universe will be caught in this phase. The detection of
WR-driven N/O enhancement at high redshift thus reflects a brief evolutionary stage
where intense, rapid feedback from a large number of WN stars briefly imprints nonuniform
elemental enrichment patterns (i.e., elevated N/O), which are expected to be quickly
washed away. As soon as the system evolves beyond the WN phase, subsequent WC or
CCSN yields will rapidly dilute the N excess and alter the overall abundance patter
(e.g., increasing C/O, lowering N/C).\r\n\r\nRecently, M. W. Topping et al. (2025b)
showed that galaxies with significant N iv] emission (corresponding to extreme N/O
enhancement), are found exclusively among galaxies with extreme [O iii]+Hβ EWs of
2600–4200 Å. Galaxies with such high [O iii]+Hβ EWs are in the upper 2% tail of
the EW distribution at z ≳ 4 and are outliers at z ∼ 0. This strongly suggests that
high N/O outliers are confined to the youngest stellar populations undergoing their
most intense bursts of star formation in the early Universe (e.g., R. Endsley et
al. 2023, 2025; J. Matthee et al. 2023; M. W. Topping et al. 2025b).\r\n\r\nIn this
context, M. W. Topping et al. (2025b) found that 30% of galaxies with EW[O III]
+ Hβ > 2000 Å show strong nitrogen emission, corresponding to ∼0.6% of their UV-selected
parent population. If this 0.6% population corresponds to enhanced N/O during the
ΔtWN ∼ 0.3 Myr WN phase, it would imply a characteristic burst timescale of ∼50
Myr. A practical consequence is that young bursts substantially increase the light-to-mass
ratios and, thus, the likelihood of detection in flux-limited samples (e.g., C.
A. Mason et al. 2023; J. B. Muñoz et al. 2023; G. Sun et al. 2023). Therefore, the
observed frequency of strong nitrogen emitters at fixed MUV is likely biased high
relative to their intrinsic abundance (e.g., at fixed stellar mass). Given the detectability
bias toward burst phases, this tburst may represent a lower limit, with the true
interval plausibly longer. This timescale is supported by recent analyses of the
scatter in the star-forming main sequence and time-resolved SFR indicators at z
∼ 3–9 that suggest burst cycles of tens-of-megayear timescales (albeit with broad
distributions, e.g., C. Simmonds et al. 2025). Thus, the combination of extreme-EW
selection and N iv] frequency provides a novel timing argument that WN-driven enrichment
is tightly coupled to very young, transient starburst phases beyond cosmic noon.\r\n\r\nTaken
together, the arguments presented in this work suggest that nitrogen outliers are
not exotic exceptions, but rather a brief, WN-enriched phase that any high-redshift
galaxy with sufficiently high SFR surface density can pass through. In contrast,
numerous low-redshift WR galaxies exhibit young populations that include WN and
WC stars but show little or no N/O enhancement (e.g., Y. I. Izotov et al. 2006;
C. Kehrig et al. 2013). This difference underscores that similar stellar populations
do not guarantee the same chemical signatures; instead, the extreme densities, compactness,
and rapid mixing timescales of high-redshift starbursts likely make WN-driven enrichment
both more pronounced and more transient. In this view, N/O outliers in the early
Universe are not anomalies, but rather are the chemical fingerprints of galaxies
caught midburst, showing fleeting yet inevitable markers of early galaxy evolution.\r\n\r\n6.
Conclusions\r\nWe have presented a detailed enrichment scenario by WN stars that
explains the extreme nitrogen enrichment in the metal-poor (∼10% Z⊙), high surface-density
(1.34 × 103 M⊙ pc−2), high-redshift (z = 6.1025), lensed galaxy RXCJ2248-ID3. These
measurements were made possible by exceptionally deep JWST/NIRSpec medium-resolution
spectroscopy of RXCJ2248-ID3, obtained as part of the GLIMPSE-D survey. The unprecedented
depth and S/N of the GLIMPSE-D spectrum allow spectral measurements typically limited
to the nearby Universe, including consistent broad components in the Balmer series
and [O iii] λ4364 and λλ4960,5008 lines, faint [Ar iv] λλ4713,4741 emission, and
signatures of WR stars. Specifically, we detected the emission characteristic of
WN-type stars, including strong N iii λ4642 and broadened He ii λ1640 and λ4687
emission, marking RXCJ2248-ID3 as the most distant galaxy to date with spectroscopic
detections of WR stars.\r\n\r\nWe performed a detailed nebular analysis, self-consistently
measuring the reddening, high-ionization temperature (Te(O+2)), and densities from
five different diagnostics across a wide ionization range. We measure a low reddening
value of from the Hγ/Hβ ratio but find an excess in the Hα/Hβ ratio of 0.204 due
to collisional excitation of Hα. The measured densities span the range of 1.15 ×
103 cm−3 ≤ ne ≤ 2.65 × 105 cm−3 and show strong evidence for nebular density stratification,
with systematically higher densities in the highest-ionization gas and UV emission
tracing gas at higher densities than those traced by optical diagnostics. This structure
implies a highly clumpy, multiphase ISM. We note that such high-density, multiphase
gas leads to densities from optical diagnostics that are biased to the low end of
the density range due to their low critical densities. Therefore, we recommend using
UV density diagnostics because they are more robust in high-density environments:
ne(Si+2), ne(C+2), and ne(N+3) trace the densities in the low-, intermediate-, and
high-ionization gas, respectively. As a result, we measure a direct-method metallicity
of .\r\n\r\nUsing the full rest-UV+optical spectra, we present the first robust,
consistent measurements of N/O abundance in any galaxy using three ionization stages
of nitrogen (N+/O+, N+2/O+2, N+3/O+2). The uniformity of our N/O measurements suggests
that the N/O enrichment is spatially extended and well mixed throughout the ionized
ISM. Empirical trends suggest C/O should follow a similar trend as N/O, and thus
also be enhanced. In contrast, we find C/O to be significantly depleted relative
to N/O, suggesting nonuniform elemental enrichment likely driven by WN stars with
little to no contribution from WC stars.\r\n\r\nThe CNO abundance pattern is best
reproduced by a modified version of the dual-burst chemical evolution model from
C. Kobayashi & A. Ferrara (2024) that reduces the contribution from WC stars relative
to WN stars, as expected in metal-poor environments. The resulting short-lived WN
phase ejects N-rich, C-poor material. We use this chemical evolution model to assess
whether the observed N mass can plausibly arise from the recent star formation in
RXCJ2248-ID3 and estimate an ionized N mass of 435 M⊙. This value is consistent
with the N mass estimated from the observed emission lines of M⊙ if % of the N gas
is ionized.\r\n\r\nThese results demonstrate that standard stellar evolution models
can reproduce both the CNO pattern and the total nitrogen mass observed without
invoking an exotic IMF or enrichment channel. The uniform N/O ratios across multiple
ionization zones further suggest that the WN yields were rapidly mixed into a relatively
pristine ambient ISM, preserving the global enhancement observed in RXCJ2248-ID3.
Although RXCJ2248-ID3 exhibits strong density and temperature stratification, this
structural complexity does not necessarily imply chemical inhomogeneity. The consistent
N/O ratios across ions tracing vastly different physical conditions indicate that
the enriched material was efficiently dispersed throughout the multiphase ISM. In
such a compact (Re ≈ 20 pc), high-pressure environment, turbulent and radiative
mixing can homogenize the chemical composition on timescales comparable to, or shorter
than, the brief WN phase itself, yielding a chemically uniform yet physically clumpy
nebula.\r\n\r\nImportantly, the abundance pattern and physical conditions observed
in RXCJ2248-ID3 can only be explained if the galaxy is caught during a narrow evolutionary
window within a few megayears of a massive, compact starburst when WN stars dominate
chemical feedback. At low metallicity, stars require higher initial masses to reach
the WR phase, making such enrichment episodes rare and dependent on sufficiently
high SFRs to fully populate the upper IMF. Furthermore, the WN phase itself is extremely
short-lived (∼0.03–0.3 Myr) and easily masked by subsequent WC winds, CCSNe, or
AGB stars contributions. These timing and SFR constraints make WR-driven N/O enhancement
a rare phenomenon associated with extreme starburst conditions that are more common
in the early Universe, and which are scarce in the local Universe.\r\n\r\nOur results
suggest that the WN-driven N/O enrichment we observe is not a peculiar property
of a single system, but rather a brief phase that essentially all high-redshift
galaxies (z > 5) with sufficiently high SFR surface densities to produce significant
numbers of WN stars likely undergo. In particular, the work of M. W. Topping et
al. (2025b) can be used to link N/O outliers to the most extreme [O iii]+Hβ EWs.
The observed frequency of such EWs combined with the short lifetime of the WN phase
implies a burst cycle of order ∼50 Myr, consistent with galaxies repeatedly cycling
through short, bursty episodes of enrichment. Thus, the GLIMPSE-D spectrum of RXCJ2248-ID3
provides not only the first direct evidence of WN stars shaping the chemical evolution
of z > 5 galaxies but also a timing argument that situates N/O outliers as a natural,
fleeting, phase of high-redshift star formation.\r\n\r\nTaken together, our findings
are a glimpse into a short-lived phase of chemically selective enrichment from WN
stars at cosmic dawn, providing a physically self-consistent solution to the extreme
N/O enhancement and relative C/O depletion observed in RXCJ2248-ID3 and galaxies
like it. Thus, RXCJ2248-ID3 serves as a benchmark case for interpreting chemically
enriched, stratified, multiphase starbursts in the early Universe.\r\n\r\nAcknowledgments\r\nWe
thank the referee for their thorough review of our calculations and analysis and
for their helpful suggestions, which greatly improved the robustness of our results
and the clarity of the text. This work is based on observations made with the NASA/ESA/CSA
James Webb Space Telescope. The data were obtained from the Mikulski Archive for
Space Telescopes at the Space Telescope Science Institute, which is operated by
the Association of Universities for Research in Astronomy, Inc., under NASA contract
NAS 5-03127 for JWST. These observations are associated with program #9223. This
work has received funding from the Swiss State Secretariat for Education, Research
and Innovation (SERI) under contract No. MB22.00072, as well as from the Swiss National
Science Foundation (SNSF) through project grant 200020_207349. The Cosmic Dawn Center
(DAWN) is funded by the Danish National Research Foundation under grant DNRF140.
The Dunlap Institute is funded through an endowment established by the David Dunlap
family and the University of Toronto. We acknowledge the support of the Canadian
Space Agency (CSA) [25JWGO4A06]. HA acknowledges support from CNES, focused on the
JWST mission, and the Programme National Cosmology and Galaxies (PNCG) of CNRS/INSU
with INP and IN2P3, co-funded by CEA and CNES and support by the French National
Research Agency (ANR) under grant ANR-21-CE31-0838. The JWST data presented in this
article from program #9223 were obtained from the Mikulski Archive for Space Telescopes
(MAST) at the Space Telescope Science Institute. The specific observations analyzed
can be accessed via DOI: 10.17909/8642-1k68."
article_number: '112'
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Danielle A.
full_name: Berg, Danielle A.
last_name: Berg
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: John
full_name: Chisholm, John
last_name: Chisholm
- first_name: Hakim
full_name: Atek, Hakim
last_name: Atek
- first_name: Seiji
full_name: Fujimoto, Seiji
last_name: Fujimoto
- first_name: Vasily
full_name: Kokorev, Vasily
last_name: Kokorev
- first_name: Lukas J.
full_name: Furtak, Lukas J.
last_name: Furtak
- first_name: Chiaki
full_name: Kobayashi, Chiaki
last_name: Kobayashi
- first_name: Daniel
full_name: Schaerer, Daniel
last_name: Schaerer
- first_name: Angela
full_name: Adamo, Angela
last_name: Adamo
- first_name: Qinyue
full_name: Fei, Qinyue
last_name: Fei
- first_name: Damien
full_name: Korber, Damien
last_name: Korber
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Rui
full_name: Marques-Chaves, Rui
last_name: Marques-Chaves
- first_name: Zorayda
full_name: Martinez, Zorayda
last_name: Martinez
- first_name: Kristen B.W.
full_name: Mcquinn, Kristen B.W.
last_name: Mcquinn
- first_name: Julian B.
full_name: Muñoz, Julian B.
last_name: Muñoz
- first_name: Pascal A.
full_name: Oesch, Pascal A.
last_name: Oesch
- first_name: Alberto
full_name: Saldana-Lopez, Alberto
last_name: Saldana-Lopez
- first_name: Daniel P.
full_name: Stark, Daniel P.
last_name: Stark
- first_name: Mabel G.
full_name: Stephenson, Mabel G.
last_name: Stephenson
- first_name: Tiger Yu Yang
full_name: Hsiao, Tiger Yu Yang
last_name: Hsiao
citation:
ama: 'Berg DA, Naidu RP, Chisholm J, et al. A fleeting GLIMPSE of N/O enrichment
at cosmic dawn: Evidence for Wolf Rayet N stars in a z = 6.1 galaxy. The Astrophysical
Journal. 2026;1003(2). doi:10.3847/1538-4357/ae5e4c'
apa: 'Berg, D. A., Naidu, R. P., Chisholm, J., Atek, H., Fujimoto, S., Kokorev,
V., … Hsiao, T. Y. Y. (2026). A fleeting GLIMPSE of N/O enrichment at cosmic dawn:
Evidence for Wolf Rayet N stars in a z = 6.1 galaxy. The Astrophysical Journal.
IOP Publishing. https://doi.org/10.3847/1538-4357/ae5e4c'
chicago: 'Berg, Danielle A., Rohan P. Naidu, John Chisholm, Hakim Atek, Seiji Fujimoto,
Vasily Kokorev, Lukas J. Furtak, et al. “A Fleeting GLIMPSE of N/O Enrichment
at Cosmic Dawn: Evidence for Wolf Rayet N Stars in a z = 6.1 Galaxy.” The Astrophysical
Journal. IOP Publishing, 2026. https://doi.org/10.3847/1538-4357/ae5e4c.'
ieee: 'D. A. Berg et al., “A fleeting GLIMPSE of N/O enrichment at cosmic
dawn: Evidence for Wolf Rayet N stars in a z = 6.1 galaxy,” The Astrophysical
Journal, vol. 1003, no. 2. IOP Publishing, 2026.'
ista: 'Berg DA, Naidu RP, Chisholm J, Atek H, Fujimoto S, Kokorev V, Furtak LJ,
Kobayashi C, Schaerer D, Adamo A, Fei Q, Korber D, Matthee JJ, Marques-Chaves
R, Martinez Z, Mcquinn KBW, Muñoz JB, Oesch PA, Saldana-Lopez A, Stark DP, Stephenson
MG, Hsiao TYY. 2026. A fleeting GLIMPSE of N/O enrichment at cosmic dawn: Evidence
for Wolf Rayet N stars in a z = 6.1 galaxy. The Astrophysical Journal. 1003(2),
112.'
mla: 'Berg, Danielle A., et al. “A Fleeting GLIMPSE of N/O Enrichment at Cosmic
Dawn: Evidence for Wolf Rayet N Stars in a z = 6.1 Galaxy.” The Astrophysical
Journal, vol. 1003, no. 2, 112, IOP Publishing, 2026, doi:10.3847/1538-4357/ae5e4c.'
short: D.A. Berg, R.P. Naidu, J. Chisholm, H. Atek, S. Fujimoto, V. Kokorev, L.J.
Furtak, C. Kobayashi, D. Schaerer, A. Adamo, Q. Fei, D. Korber, J.J. Matthee,
R. Marques-Chaves, Z. Martinez, K.B.W. Mcquinn, J.B. Muñoz, P.A. Oesch, A. Saldana-Lopez,
D.P. Stark, M.G. Stephenson, T.Y.Y. Hsiao, The Astrophysical Journal 1003 (2026).
date_created: 2026-05-31T22:02:12Z
date_published: 2026-05-20T00:00:00Z
date_updated: 2026-06-02T08:46:20Z
day: '20'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.3847/1538-4357/ae5e4c
external_id:
arxiv:
- '2511.13591'
file:
- access_level: open_access
checksum: 1058555fdede45e10fca25d74e7977bc
content_type: application/pdf
creator: dernst
date_created: 2026-06-02T08:46:08Z
date_updated: 2026-06-02T08:46:08Z
file_id: '21938'
file_name: 2026_AstrophysicalJour_Berg.pdf
file_size: 21249354
relation: main_file
success: 1
file_date_updated: 2026-06-02T08:46:08Z
has_accepted_license: '1'
intvolume: ' 1003'
issue: '2'
language:
- iso: eng
month: '05'
oa: 1
oa_version: Published Version
publication: The Astrophysical Journal
publication_identifier:
eissn:
- 1538-4357
issn:
- 0004-637X
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'A fleeting GLIMPSE of N/O enrichment at cosmic dawn: Evidence for Wolf Rayet
N stars in a z = 6.1 galaxy'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 1003
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: diamond
PlanS_conform: '1'
_id: '21951'
abstract:
- lang: eng
text: "The central engines of Little Red Dots (LRDs) may be “black hole stars” (BH*s),
early stages of\r\nblack hole growth characterized by dense gas envelopes. So
far, the most direct evidence for BH*s\r\ncomes from a handful of sources where
the host galaxy is completely outshone as suggested by their\r\nremarkably steep
Balmer breaks. Here we present a novel scheme to disentangle BH*s from their\r\nhost
galaxies assuming that the [O III]5008˚A line arises exclusively from the host.
Using a sample\r\nof 98 LRDs (z ≈ 2 − 9) with high quality NIRSpec/PRISM spectra,
we demonstrate that the hostsubtracted median stack displays a Balmer break >
2× stronger than massive quiescent galaxies,\r\nwith the rest-optical continuum
resembling a blackbody-like SED (Teff ≈ 4050 K, log(Lbol) ≈ 43.9\r\nerg s−1\r\n,
Reff ≈ 1300 au). We measure a steep Balmer decrement (Hα/Hβ > 10) and numerous\r\ndensity-sensitive
features (e.g., Fe II, He I, O I). These are hallmark signatures of dense gas
envelopes,\r\nproviding population-level evidence that BH*s indeed power LRDs.
In the median LRD, BH*s account\r\nfor ∼ 20% of the UV emission, ∼ 50% at the
Balmer break, and ∼ 90% at wavelengths longer\r\nthan Hα with the remainder arising
from the host. BH*s preferentially reside in low-mass galaxies\r\n(M⋆ ≈ 108 M⊙)
undergoing recent starbursts, as evidenced by extreme emission line EWs (e.g.,\r\n[O
III]5008˚A≈ 1100˚A, C III]≈ 12˚A), thereby favoring BH* origins linked to star-formation.
We show\r\nV-shaped LRD selections are biased to high BH*/host fractions (≳ 60%
at 5500˚A) – less dominant\r\nBH*s may be powering JWST’s blue broad-line AGN.
We find BH*s are so commonplace and transient\r\n(duty cycle ∼ 1%, lifetime ∼
10 Myrs) that every massive black hole may have once shone as a BH*.\r\n"
acknowledgement: "We thank the two anonymous referees for their insightful comments
that have strengthened this work.\r\nWQS and RPN acknowledge funding from JWST programs
GO-3516, GO-5224, and the MIT Undergraduate\r\nResearch Opportunities Program (UROP).
Support for\r\nthis work was provided by NASA through the NASA\r\nHubble Fellowship
grant HST-HF2-51515.001-A awarded\r\nby the Space Telescope Science Institute, which
is operated by the Association of Universities for Research in\r\nAstronomy, Incorporated,
under NASA contract NAS5-\r\n26555. RPN thanks Neil Pappalardo and Jane Pappalardo
for their generous support of the MIT Pappalardo Fellowships in Physics, and for
their enthusiasm\r\nand encouragement for pursuing the earliest galaxies and\r\nblack
holes. JM and AT acknowledge funding from the\r\nEuropean Union (ERC, AGENTS, 101076224).
KEH\r\nacknowledges support from the Independent Research Fund Denmark (DFF) under
grant 5251-00009B and cofunding by the European Union (ERC, HEAVYMETAL,\r\n101071865).
Views and opinions expressed are, however,\r\nthose of the authors only and do not
necessarily reflect\r\nthose of the European Union or the European Research\r\nCouncil.
Neither the European Union nor the granting\r\nauthority can be held responsible
for them. REH acknowledges support by the German Aerospace Center\r\n(DLR) and the
Federal Ministry for Economic Affairs\r\nand Energy (BMWi) through program 50OR2403
‘RUBIES’.\r\nThe data products presented herein were retrieved\r\nfrom the Dawn
JWST Archive (DJA). DJA is an initiative of the Cosmic Dawn Center (DAWN), which
is\r\nfunded by the Danish National Research Foundation under grant DNRF140. This
work is based on observations\r\nmade with the NASA/ESA/CSA James Webb Space\r\nTelescope.
The data were obtained from the Mikulski Archive for Space Telescopes at the Space
Telescope\r\nScience Institute, which is operated by the Association\r\nof Universities
for Research in Astronomy, Inc., under\r\nNASA contract NAS 5-03127 for JWST. Support
for\r\nprograms #3516, #5224, #5664 was provided by NASA\r\nthrough grants from
the Space Telescope Science Institute, which is operated by the Association of Universities\r\nfor
Research in Astronomy, Inc., under NASA contract\r\nNAS 5-03127.\r\nThe spectra
used in this paper are associated with programs 1180 (D’Eugenio et al. 2025d), 1181
(PI: D. Eisenstein), 1208 (Willott et al. 2022), 1210 (PI: N. Luetzgendorf), 1211
(Maseda et al. 2024), 1212 - 1215 (PI: N.\r\nLuetzgendorf), 1228 (Luhman et al.
2024b), 1229 (Luhman et al. 2024a), 1286 (PI: N. Luetzgendorf), 1287 (PI:\r\nK.
Isaak), 1345 (Finkelstein et al. 2023), 1433 (Hsiao\r\net al. 2024), 1747 (PI: G.
Roberts-Borsani), 2028 (Wang\r\net al. 2024c), 2073 (PI: J. Hennawi), 2198 (Barrufet\r\net
al. 2025), 2282 (Bradley et al. 2023), 2561 (Bezanson\r\net al. 2024), 2565 (Nanayakkara
et al. 2025), 2640 (PI:\r\nW. Best), 2750 (Arrabal Haro et al. 2023), 2756 (Mascia
et al. 2024), 2767 (Williams et al. 2023b), 2770 (PI:\r\nM. McCaughrean), 3073 (Castellano
et al. 2024), 3215\r\n(Eisenstein et al. 2025), 4106 (PI: E. Nelson), 4233 (de\r\nGraaff
et al. 2025c), 4446 (Frye et al. 2024), 4557 (PI: H.\r\nYan), 5105 (Shen et al.
2024), 5224 (PIs: P.A. Oesch &\r\nR.P. Naidu), 6368 (PI: M. Dickinson), 6541 (DeCoursey\r\net
al. 2025), 6585 (PI: D. Coulter), 6642 (PI: J. Muzerolle\r\nPage), and FRESCO IFU
(Matthee et al. 2024; Torralba\r\net al. 2025b).\r\nSoftware used in developing
this work includes:\r\nmatplotlib (Hunter 2007), jupyter (Kluyver et al.\r\n2016),
IPython (P´erez & Granger 2007), numpy\r\n(Oliphant 2015), scipy (Virtanen et al.
2020), TOPCAT\r\n(Taylor 2005), Astropy (Astropy Collaboration et al.\r\n2013),
msaexp (Brammer 2023)."
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Wendy Q.
full_name: Sun, Wendy Q.
last_name: Sun
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Anna
full_name: De Graaff, Anna
last_name: De Graaff
- first_name: John
full_name: Chisholm, John
last_name: Chisholm
- first_name: Jenny E.
full_name: Greene, Jenny E.
last_name: Greene
- first_name: Pascal A.
full_name: Oesch, Pascal A.
last_name: Oesch
- first_name: Alberto
full_name: Torralba Torregrosa, Alberto
id: 018f0249-0e87-11f0-b167-cbce08fbd541
last_name: Torralba Torregrosa
orcid: 0000-0001-5586-6950
- first_name: Raphael E.
full_name: Hviding, Raphael E.
last_name: Hviding
- first_name: Gabriel
full_name: Brammer, Gabriel
last_name: Brammer
- first_name: Robert A.
full_name: Simcoe, Robert A.
last_name: Simcoe
- first_name: Sownak
full_name: Bose, Sownak
last_name: Bose
- first_name: Rychard
full_name: Bouwens, Rychard
last_name: Bouwens
- first_name: Pratika
full_name: Dayal, Pratika
last_name: Dayal
- first_name: Anna Christina
full_name: Eilers, Anna Christina
last_name: Eilers
- first_name: Qinyue
full_name: Fei, Qinyue
last_name: Fei
- first_name: Lukas J.
full_name: Furtak, Lukas J.
last_name: Furtak
- first_name: Rashmi
full_name: Gottumukkala, Rashmi
last_name: Gottumukkala
- first_name: Andy
full_name: Goulding, Andy
last_name: Goulding
- first_name: Kasper E.
full_name: Heintz, Kasper E.
last_name: Heintz
- first_name: Michaela
full_name: Hirschmann, Michaela
last_name: Hirschmann
- first_name: Vasily
full_name: Kokorev, Vasily
last_name: Kokorev
- first_name: Joel
full_name: Leja, Joel
last_name: Leja
- first_name: Zhaoran
full_name: Liu, Zhaoran
last_name: Liu
- first_name: Priyamvada
full_name: Natarajan, Priyamvada
last_name: Natarajan
- first_name: Andrew D.
full_name: Santarelli, Andrew D.
last_name: Santarelli
- first_name: David J.
full_name: Setton, David J.
last_name: Setton
- first_name: Aaron
full_name: Smith, Aaron
last_name: Smith
- first_name: Sandro
full_name: Tacchella, Sandro
last_name: Tacchella
- first_name: Marta
full_name: Volonteri, Marta
last_name: Volonteri
- first_name: Fabian
full_name: Walter, Fabian
last_name: Walter
- first_name: Andrea
full_name: Weibel, Andrea
last_name: Weibel
- first_name: Christina C.
full_name: Williams, Christina C.
last_name: Williams
citation:
ama: 'Sun WQ, Naidu RP, Matthee JJ, et al. Little Red Dot - Host Galaxy = Black
Hole Star: A gas-enshrouded heart at the center of every Little Red Dot. The
Open Journal of Astrophysics. 2026;9. doi:10.33232/001c.162505'
apa: 'Sun, W. Q., Naidu, R. P., Matthee, J. J., De Graaff, A., Chisholm, J., Greene,
J. E., … Williams, C. C. (2026). Little Red Dot - Host Galaxy = Black Hole Star:
A gas-enshrouded heart at the center of every Little Red Dot. The Open Journal
of Astrophysics. Maynooth Academic Publishing. https://doi.org/10.33232/001c.162505'
chicago: 'Sun, Wendy Q., Rohan P. Naidu, Jorryt J Matthee, Anna De Graaff, John
Chisholm, Jenny E. Greene, Pascal A. Oesch, et al. “Little Red Dot - Host Galaxy
= Black Hole Star: A Gas-Enshrouded Heart at the Center of Every Little Red Dot.”
The Open Journal of Astrophysics. Maynooth Academic Publishing, 2026. https://doi.org/10.33232/001c.162505.'
ieee: 'W. Q. Sun et al., “Little Red Dot - Host Galaxy = Black Hole Star:
A gas-enshrouded heart at the center of every Little Red Dot,” The Open Journal
of Astrophysics, vol. 9. Maynooth Academic Publishing, 2026.'
ista: 'Sun WQ, Naidu RP, Matthee JJ, De Graaff A, Chisholm J, Greene JE, Oesch PA,
Torralba Torregrosa A, Hviding RE, Brammer G, Simcoe RA, Bose S, Bouwens R, Dayal
P, Eilers AC, Fei Q, Furtak LJ, Gottumukkala R, Goulding A, Heintz KE, Hirschmann
M, Kokorev V, Leja J, Liu Z, Natarajan P, Santarelli AD, Setton DJ, Smith A, Tacchella
S, Volonteri M, Walter F, Weibel A, Williams CC. 2026. Little Red Dot - Host Galaxy
= Black Hole Star: A gas-enshrouded heart at the center of every Little Red Dot.
The Open Journal of Astrophysics. 9.'
mla: 'Sun, Wendy Q., et al. “Little Red Dot - Host Galaxy = Black Hole Star: A Gas-Enshrouded
Heart at the Center of Every Little Red Dot.” The Open Journal of Astrophysics,
vol. 9, Maynooth Academic Publishing, 2026, doi:10.33232/001c.162505.'
short: W.Q. Sun, R.P. Naidu, J.J. Matthee, A. De Graaff, J. Chisholm, J.E. Greene,
P.A. Oesch, A. Torralba Torregrosa, R.E. Hviding, G. Brammer, R.A. Simcoe, S.
Bose, R. Bouwens, P. Dayal, A.C. Eilers, Q. Fei, L.J. Furtak, R. Gottumukkala,
A. Goulding, K.E. Heintz, M. Hirschmann, V. Kokorev, J. Leja, Z. Liu, P. Natarajan,
A.D. Santarelli, D.J. Setton, A. Smith, S. Tacchella, M. Volonteri, F. Walter,
A. Weibel, C.C. Williams, The Open Journal of Astrophysics 9 (2026).
date_created: 2026-06-07T22:01:36Z
date_published: 2026-05-25T00:00:00Z
date_updated: 2026-06-08T08:25:40Z
day: '25'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.33232/001c.162505
external_id:
arxiv:
- '2601.20929'
file:
- access_level: open_access
checksum: 33c4a444f7c37b3f47ecbd53eb187c1b
content_type: application/pdf
creator: dernst
date_created: 2026-06-08T08:23:37Z
date_updated: 2026-06-08T08:23:37Z
file_id: '21952'
file_name: 2026_OpenJourAstrophysics_Sun.pdf
file_size: 7591188
relation: main_file
success: 1
file_date_updated: 2026-06-08T08:23:37Z
has_accepted_license: '1'
intvolume: ' 9'
language:
- iso: eng
month: '05'
oa: 1
oa_version: Published Version
project:
- _id: bd9b2118-d553-11ed-ba76-db24564edfea
grant_number: '101076224'
name: Young galaxies as tracers and agents of cosmic reionization
publication: The Open Journal of Astrophysics
publication_identifier:
eissn:
- 2565-6120
publication_status: published
publisher: Maynooth Academic Publishing
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'Little Red Dot - Host Galaxy = Black Hole Star: A gas-enshrouded heart at
the center of every Little Red Dot'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 9
year: '2026'
...
---
OA_place: publisher
OA_type: diamond
PlanS_conform: '1'
_id: '21045'
abstract:
- lang: eng
text: 'The abundant population of little red dots (LRDs), compact objects with red
UV to optical colors and broad Balmer lines at high redshift, is revealing new
insights into the properties of early active galactic nuclei (AGN). Perhaps the
most surprising features of this population are the presence of Balmer absorption
and ubiquitous strong Balmer breaks. Recent models link these features to an active
supermassive black hole (SMBH) cocooned in very dense gas (NH ∼ 1024 cm−2). We
present a stringent test of such models using VLT/MUSE observations of A2744-45924,
the most luminous LRD known to date (LHα ≈ 1044 erg s−1), located behind the Abell-2744
lensing cluster at z = 4.464 (μ = 1.8). We detect a moderately extended Lyα nebula
(h ≈ 5.7 pkpc), spatially offset from the point-like Hα seen by JWST by ≈1.6 pkpc.
The Lyα emission is narrow (FWHM = 270 ± 15 km s−1), and faint (Lyα = 0.07Hα)
compared to Lyα nebulae typically observed around quasars of similar luminosity.
We detect compact N IV]λ1486 emission, spatially aligned with Hα, and a spatial
shift in the far-UV continuum matching the Lyα offset. We discuss that Hα and
Lyα have distinct physical origins: Hα originates from the AGN, while Lyα is powered
by star formation. In the environment of A2744-45924, we identified four extended
Lyα halos (Δz < 0.02, Δr < 100 pkpc). Their Lyα luminosities match the expectations
based on Hα emission, and show no evidence for radiation from A2744-45924 affecting
its surroundings. The lack of strong, compact, and broad Lyα and the absence of
a luminous extended halo, suggest that the UV AGN light is obscured by dense gas
cloaking the SMBH with a covering factor close to unity.'
acknowledgement: 'We thank the anonymous referee for constructive and useful comments.
We thank Sebastiano Cantalupo for comments on the draft. Based on observations collected
at the European Organisation for Astronomical Research in the Southern Hemisphere
under ESO programme 114.27M6.001. Funded by the European Union (ERC, AGENTS, 101076224).
Views and opinions expressed are however those of the author(s) only and do not
necessarily reflect those of the European Union or the European Research Council.
Neither the European Union nor the granting authority can be held responsible for
them. We acknowledge funding from JWST program GO-3516. This work is based in part
on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data
were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope
Science Institute, which is operated by the Association of Universities for Research
in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations
are associated with program #3516. MG thanks the Max Planck Society for support
through the MPRG. FDE acknowledges support by the Science and Technology Facilities
Council (STFC), by the ERC through Advanced Grant 695671 “QUENCH”, and by the UKRI
Frontier Research grant RISEandFALL. TU acknowledges funding from the ERC-AdG grant
SPECMAP-CGM, GA 101020943. GK acknowledges support from the MERAC foundation.'
article_number: A147
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Alberto
full_name: Torralba Torregrosa, Alberto
id: 018f0249-0e87-11f0-b167-cbce08fbd541
last_name: Torralba Torregrosa
orcid: 0000-0001-5586-6950
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Gabriele
full_name: Pezzulli, Gabriele
last_name: Pezzulli
- first_name: Tanya
full_name: Urrutia, Tanya
last_name: Urrutia
- first_name: Max
full_name: Gronke, Max
last_name: Gronke
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: Francesco
full_name: D’Eugenio, Francesco
last_name: D’Eugenio
- first_name: Claudia
full_name: Di Cesare, Claudia
id: 2d002343-372f-11ef-98ec-a164d20427cb
last_name: Di Cesare
- first_name: Anna Christina
full_name: Eilers, Anna Christina
last_name: Eilers
- first_name: Jenny E.
full_name: Greene, Jenny E.
last_name: Greene
- first_name: Edoardo
full_name: Iani, Edoardo
id: 4053390a-6b68-11ef-9828-a3b8adef8d0a
last_name: Iani
orcid: 0000-0001-8386-3546
- first_name: Yuzo
full_name: Ishikawa, Yuzo
last_name: Ishikawa
- first_name: Ruari
full_name: Mackenzie, Ruari
last_name: Mackenzie
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: Benjamín
full_name: Navarrete, Benjamín
id: aa14a535-50c9-11ef-b52e-e0c373d10148
last_name: Navarrete
- first_name: Gauri
full_name: Kotiwale, Gauri
id: 1438afc8-1ff6-11ee-9fa6-cd4a75d66875
last_name: Kotiwale
citation:
ama: Torralba Torregrosa A, Matthee JJ, Pezzulli G, et al. A weak Ly α halo for
an extremely bright little red dot. Indications of enshrouded supermassive black
hole growth. Astronomy & Astrophysics. 2026;705. doi:10.1051/0004-6361/202555596
apa: Torralba Torregrosa, A., Matthee, J. J., Pezzulli, G., Urrutia, T., Gronke,
M., Mascia, S., … Kotiwale, G. (2026). A weak Ly α halo for an extremely bright
little red dot. Indications of enshrouded supermassive black hole growth. Astronomy
& Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/202555596
chicago: Torralba Torregrosa, Alberto, Jorryt J Matthee, Gabriele Pezzulli, Tanya
Urrutia, Max Gronke, Sara Mascia, Francesco D’Eugenio, et al. “A Weak Ly α Halo
for an Extremely Bright Little Red Dot. Indications of Enshrouded Supermassive
Black Hole Growth.” Astronomy & Astrophysics. EDP Sciences, 2026. https://doi.org/10.1051/0004-6361/202555596.
ieee: A. Torralba Torregrosa et al., “A weak Ly α halo for an extremely bright
little red dot. Indications of enshrouded supermassive black hole growth,” Astronomy
& Astrophysics, vol. 705. EDP Sciences, 2026.
ista: Torralba Torregrosa A, Matthee JJ, Pezzulli G, Urrutia T, Gronke M, Mascia
S, D’Eugenio F, Di Cesare C, Eilers AC, Greene JE, Iani E, Ishikawa Y, Mackenzie
R, Naidu RP, Navarrete B, Kotiwale G. 2026. A weak Ly α halo for an extremely
bright little red dot. Indications of enshrouded supermassive black hole growth.
Astronomy & Astrophysics. 705, A147.
mla: Torralba Torregrosa, Alberto, et al. “A Weak Ly α Halo for an Extremely Bright
Little Red Dot. Indications of Enshrouded Supermassive Black Hole Growth.” Astronomy
& Astrophysics, vol. 705, A147, EDP Sciences, 2026, doi:10.1051/0004-6361/202555596.
short: A. Torralba Torregrosa, J.J. Matthee, G. Pezzulli, T. Urrutia, M. Gronke,
S. Mascia, F. D’Eugenio, C. Di Cesare, A.C. Eilers, J.E. Greene, E. Iani, Y. Ishikawa,
R. Mackenzie, R.P. Naidu, B. Navarrete, G. Kotiwale, Astronomy & Astrophysics
705 (2026).
corr_author: '1'
das_tickbox: '1'
date_created: 2026-01-25T23:01:41Z
date_published: 2026-01-14T00:00:00Z
date_updated: 2026-07-08T06:38:23Z
day: '14'
ddc:
- '520'
department:
- _id: JoMa
- _id: GradSch
doi: 10.1051/0004-6361/202555596
external_id:
arxiv:
- '2505.09542'
file:
- access_level: open_access
checksum: 3782e03bc0843438aae8487f6af779c5
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creator: dernst
date_created: 2026-02-16T07:35:03Z
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file_name: 2026_AstronomyAstrophysics_Torralba.pdf
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intvolume: ' 705'
language:
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month: '01'
oa: 1
oa_version: Published Version
project:
- _id: bd9b2118-d553-11ed-ba76-db24564edfea
grant_number: '101076224'
name: Young galaxies as tracers and agents of cosmic reionization
publication: Astronomy & Astrophysics
publication_identifier:
eissn:
- 1432-0746
issn:
- 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
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status: public
title: A weak Ly α halo for an extremely bright little red dot. Indications of enshrouded
supermassive black hole growth
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 705
year: '2026'
...
---
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OA_type: gold
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abstract:
- lang: eng
text: 'The well-known bimodality between star-forming discs and quiescent spheroids
requires the existence of two main processes: galaxy quenching, causing the strong
reduction of star formation, and morphological transformation, causing the transition
from disc-dominated structures to bulge-dominated ones. In this paper, we aim
to understand the link between these two processes and their relation with the
stellar mass of galaxies and their local environment. Taking advantage of the
first data released by the Euclid Collaboration, covering more than 60 deg2 with
space-based imaging and photometry, we analyse a mass-complete sample of nearly
one million galaxies in the range 0.25 < z < 1 with M* > 109.5 M⊙, using a combination
of photometric and spectroscopic redshifts. We divide the sample into four sub-populations
of galaxies, based on their star-formation activity (star-forming and quiescent)
and morphology (disc-dominated and bulge-dominated). We then analyse the physical
properties of these populations and their relative abundances in the stellar mass
versus local density plane. Together with confirming the passivity-density relation
and the morphology-density relation, we find that quiescent discy galaxies are
more abundant in the low-mass regime of high-density environment where log10(1 + δ)
> 1.3. At the same time, star-forming bulge-dominated galaxies are more common
in field regions with log10(1 + δ) < 0.8, preferentially at high masses. Building
on these results and interpreting them through comparison with simulations, we
propose a scenario where the evolution of galaxies in the field significantly
differs from that in higher-density environments. The morphological transformation
in the majority of field galaxies takes place before the onset of quenching and
is mainly driven by secular processes taking place within the main sequence, leading
to the formation of star-forming bulge-dominated galaxies as intermediate-stage
galaxies. Conversely, quenching of star formation precedes morphological transformation
for most galaxies in higher-density environments. This causes the formation of
quiescent disc-dominated galaxies before their transition into bulge-dominated
ones.'
acknowledgement: 'FaGe, AnEn, EmDa, LoGa, SaQu, GaDe, MaTa, ChDe, LuPo acknowledge
support from the ELSA project. “ELSA: Euclid Legacy Science Advanced analysis tools”
(Grant Agreement no. 101135203) is funded by the European Union. Views and opinions
expressed are however those of the author(s) only and do not necessarily reflect
those of the European Union or Innovate UK. Neither the European Union nor the granting
authority can be held responsible for them. UK participation is funded through the
UK HORIZON guarantee scheme under Innovate UK grant 10093177. AnEn acknowledge support
from the INAF MiniGrant 2023 “ADIEU: Anomaly Detections In EUclid”. CaLo acknowledges
support by FCT-Fundação para a Ciência e a Tecnologia through grants UIDB/04434/2020
DOI: 10.54499/UIDB/04434/2020, UIDP/04434/2020 DOI: 10.54499/UIDP/04434/2020. The
Euclid Consortium acknowledges the European Space Agency and a number of agencies
and institutes that have supported the development of Euclid, in particular the
Agenzia Spaziale Italiana, the Austrian Forschungsförderungsgesellschaft funded
through BMK, the Belgian Science Policy, the Canadian Euclid Consortium, the Deutsches
Zentrum für Luft-und Raumfahrt, the DTU Space and the Niels Bohr Institute in Denmark,
the French Centre National d’Etudes Spatiales, the Fundação para a Ciência e a Tecnologia,
the Hungarian Academy of Sciences, the Ministerio de Ciencia, Innovación y Universidades,
the National Aeronautics and Space Administration, the National Astronomical Observatory
of Japan, the Netherlandse Onderzoekschool Voor Astronomie, the Norwegian Space
Agency, the Research Council of Finland, the Romanian Space Agency, the State Secretariat
for Education, Research, and Innovation (SERI) at the Swiss Space Office (SSO),
and the United Kingdom Space Agency. A complete and detailed list is available on
the Euclid website (www.euclid-ec.org). This work has made use of the Euclid Quick
Release Q1 data from the Euclid mission of the European Space Agency (ESA), 2025,
https://doi.org/10.57780/esa-2853f3b. This work has made use of CosmoHub, developed
by PIC (maintained by IFAE and CIEMAT) in collaboration with ICE-CSIC. CosmoHub
received funding from the Spanish government (MCIN/AEI/10.13039/501100011033), the
EU NextGeneration/PRTR (PRTR-C17.I1), and the Generalitat de Catalunya. Based on
data from UNIONS, a scientific collaboration using three Hawaii-based telescopes:
CFHT, Pan-STARRS, and Subaru www.skysurvey.cc. Based on data from the Dark Energy
Camera (DECam) on the Blanco 4-m Telescope at CTIO in Chile https://www.darkenergysurvey.org'
article_number: A12
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: F.
full_name: Gentile, F.
last_name: Gentile
- first_name: E.
full_name: Daddi, E.
last_name: Daddi
- first_name: D.
full_name: Elbaz, D.
last_name: Elbaz
- first_name: A.
full_name: Enia, A.
last_name: Enia
- first_name: B.
full_name: Magnelli, B.
last_name: Magnelli
- first_name: J. B.
full_name: Billand, J. B.
last_name: Billand
- first_name: P.
full_name: Corcho-Caballero, P.
last_name: Corcho-Caballero
- first_name: C.
full_name: Cleland, C.
last_name: Cleland
- first_name: G.
full_name: De Lucia, G.
last_name: De Lucia
- first_name: C.
full_name: D’Eugenio, C.
last_name: D’Eugenio
- first_name: M.
full_name: Fossati, M.
last_name: Fossati
- first_name: M.
full_name: Franco, M.
last_name: Franco
- first_name: C.
full_name: Lobo, C.
last_name: Lobo
- first_name: Y.
full_name: Lyu, Y.
last_name: Lyu
- first_name: M.
full_name: Magliocchetti, M.
last_name: Magliocchetti
- first_name: G. A.
full_name: Mamon, G. A.
last_name: Mamon
- first_name: L.
full_name: Quilley, L.
last_name: Quilley
- first_name: J. G.
full_name: Sorce, J. G.
last_name: Sorce
- first_name: M.
full_name: Tarrasse, M.
last_name: Tarrasse
- first_name: M.
full_name: Bolzonella, M.
last_name: Bolzonella
- first_name: F.
full_name: Durret, F.
last_name: Durret
- first_name: L.
full_name: Gabarra, L.
last_name: Gabarra
- first_name: S.
full_name: Guo, S.
last_name: Guo
- first_name: L.
full_name: Pozzetti, L.
last_name: Pozzetti
- first_name: S.
full_name: Quai, S.
last_name: Quai
- first_name: F.
full_name: Shankar, F.
last_name: Shankar
- first_name: V.
full_name: Sangalli, V.
last_name: Sangalli
- first_name: M.
full_name: Talia, M.
last_name: Talia
- first_name: M.
full_name: Baes, M.
last_name: Baes
- first_name: H.
full_name: Fu, H.
last_name: Fu
- first_name: M.
full_name: Girardi, M.
last_name: Girardi
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: P. A.
full_name: Oesch, P. A.
last_name: Oesch
- first_name: D.
full_name: Roberts, D.
last_name: Roberts
- first_name: J.
full_name: Schaye, J.
last_name: Schaye
- first_name: D.
full_name: Scott, D.
last_name: Scott
- first_name: L.
full_name: Spinoglio, L.
last_name: Spinoglio
- first_name: B.
full_name: Altieri, B.
last_name: Altieri
- first_name: A.
full_name: Amara, A.
last_name: Amara
- first_name: S.
full_name: Andreon, S.
last_name: Andreon
- first_name: N.
full_name: Auricchio, N.
last_name: Auricchio
- first_name: C.
full_name: Baccigalupi, C.
last_name: Baccigalupi
- first_name: M.
full_name: Baldi, M.
last_name: Baldi
- first_name: A.
full_name: Balestra, A.
last_name: Balestra
- first_name: S.
full_name: Bardelli, S.
last_name: Bardelli
- first_name: R.
full_name: Bender, R.
last_name: Bender
- first_name: A.
full_name: Biviano, A.
last_name: Biviano
- first_name: E.
full_name: Branchini, E.
last_name: Branchini
- first_name: M.
full_name: Brescia, M.
last_name: Brescia
- first_name: J.
full_name: Brinchmann, J.
last_name: Brinchmann
- first_name: S.
full_name: Camera, S.
last_name: Camera
- first_name: G.
full_name: Cañas-Herrera, G.
last_name: Cañas-Herrera
- first_name: V.
full_name: Capobianco, V.
last_name: Capobianco
- first_name: C.
full_name: Carbone, C.
last_name: Carbone
- first_name: J.
full_name: Carretero, J.
last_name: Carretero
- first_name: S.
full_name: Casas, S.
last_name: Casas
- first_name: M.
full_name: Castellano, M.
last_name: Castellano
- first_name: G.
full_name: Castignani, G.
last_name: Castignani
- first_name: S.
full_name: Cavuoti, S.
last_name: Cavuoti
- first_name: K. C.
full_name: Chambers, K. C.
last_name: Chambers
- first_name: A.
full_name: Cimatti, A.
last_name: Cimatti
- first_name: C.
full_name: Colodro-Conde, C.
last_name: Colodro-Conde
- first_name: G.
full_name: Congedo, G.
last_name: Congedo
- first_name: L.
full_name: Conversi, L.
last_name: Conversi
- first_name: Y.
full_name: Copin, Y.
last_name: Copin
- first_name: F.
full_name: Courbin, F.
last_name: Courbin
- first_name: H. M.
full_name: Courtois, H. M.
last_name: Courtois
- first_name: M.
full_name: Cropper, M.
last_name: Cropper
- first_name: A.
full_name: Da Silva, A.
last_name: Da Silva
- first_name: H.
full_name: Degaudenzi, H.
last_name: Degaudenzi
- first_name: C.
full_name: Dolding, C.
last_name: Dolding
- first_name: H.
full_name: Dole, H.
last_name: Dole
- first_name: F.
full_name: Dubath, F.
last_name: Dubath
- first_name: C. A.J.
full_name: Duncan, C. A.J.
last_name: Duncan
- first_name: X.
full_name: Dupac, X.
last_name: Dupac
- first_name: S.
full_name: Dusini, S.
last_name: Dusini
- first_name: S.
full_name: Escoffier, S.
last_name: Escoffier
- first_name: M.
full_name: Fabricius, M.
last_name: Fabricius
- first_name: M.
full_name: Farina, M.
last_name: Farina
- first_name: R.
full_name: Farinelli, R.
last_name: Farinelli
- first_name: S.
full_name: Ferriol, S.
last_name: Ferriol
- first_name: F.
full_name: Finelli, F.
last_name: Finelli
- first_name: N.
full_name: Fourmanoit, N.
last_name: Fourmanoit
- first_name: M.
full_name: Frailis, M.
last_name: Frailis
- first_name: E.
full_name: Franceschi, E.
last_name: Franceschi
- first_name: M.
full_name: Fumana, M.
last_name: Fumana
- first_name: S.
full_name: Galeotta, S.
last_name: Galeotta
- first_name: K.
full_name: George, K.
last_name: George
- first_name: B.
full_name: Gillis, B.
last_name: Gillis
- first_name: C.
full_name: Giocoli, C.
last_name: Giocoli
- first_name: J.
full_name: Gracia-Carpio, J.
last_name: Gracia-Carpio
- first_name: A.
full_name: Grazian, A.
last_name: Grazian
- first_name: F.
full_name: Grupp, F.
last_name: Grupp
- first_name: S.
full_name: Gwyn, S.
last_name: Gwyn
- first_name: S. V.H.
full_name: Haugan, S. V.H.
last_name: Haugan
- first_name: J.
full_name: Hoar, J.
last_name: Hoar
- first_name: W.
full_name: Holmes, W.
last_name: Holmes
- first_name: I. M.
full_name: Hook, I. M.
last_name: Hook
- first_name: F.
full_name: Hormuth, F.
last_name: Hormuth
- first_name: A.
full_name: Hornstrup, A.
last_name: Hornstrup
- first_name: K.
full_name: Jahnke, K.
last_name: Jahnke
- first_name: M.
full_name: Jhabvala, M.
last_name: Jhabvala
- first_name: B.
full_name: Joachimi, B.
last_name: Joachimi
- first_name: E.
full_name: Keihänen, E.
last_name: Keihänen
- first_name: S.
full_name: Kermiche, S.
last_name: Kermiche
- first_name: A.
full_name: Kiessling, A.
last_name: Kiessling
- first_name: B.
full_name: Kubik, B.
last_name: Kubik
- first_name: M.
full_name: Kümmel, M.
last_name: Kümmel
- first_name: M.
full_name: Kunz, M.
last_name: Kunz
- first_name: H.
full_name: Kurki-Suonio, H.
last_name: Kurki-Suonio
- first_name: A. M.C.
full_name: Le Brun, A. M.C.
last_name: Le Brun
- first_name: S.
full_name: Ligori, S.
last_name: Ligori
- first_name: P. B.
full_name: Lilje, P. B.
last_name: Lilje
- first_name: V.
full_name: Lindholm, V.
last_name: Lindholm
- first_name: I.
full_name: Lloro, I.
last_name: Lloro
- first_name: G.
full_name: Mainetti, G.
last_name: Mainetti
- first_name: D.
full_name: Maino, D.
last_name: Maino
- first_name: E.
full_name: Maiorano, E.
last_name: Maiorano
- first_name: O.
full_name: Mansutti, O.
last_name: Mansutti
- first_name: O.
full_name: Marggraf, O.
last_name: Marggraf
- first_name: M.
full_name: Martinelli, M.
last_name: Martinelli
- first_name: N.
full_name: Martinet, N.
last_name: Martinet
- first_name: F.
full_name: Marulli, F.
last_name: Marulli
- first_name: R. J.
full_name: Massey, R. J.
last_name: Massey
- first_name: E.
full_name: Medinaceli, E.
last_name: Medinaceli
- first_name: S.
full_name: Mei, S.
last_name: Mei
- first_name: M.
full_name: Melchior, M.
last_name: Melchior
- first_name: Y.
full_name: Mellier, Y.
last_name: Mellier
- first_name: M.
full_name: Meneghetti, M.
last_name: Meneghetti
- first_name: E.
full_name: Merlin, E.
last_name: Merlin
- first_name: G.
full_name: Meylan, G.
last_name: Meylan
- first_name: A.
full_name: Mora, A.
last_name: Mora
- first_name: M.
full_name: Moresco, M.
last_name: Moresco
- first_name: L.
full_name: Moscardini, L.
last_name: Moscardini
- first_name: R.
full_name: Nakajima, R.
last_name: Nakajima
- first_name: S. M.
full_name: Niemi, S. M.
last_name: Niemi
- first_name: C.
full_name: Padilla, C.
last_name: Padilla
- first_name: S.
full_name: Paltani, S.
last_name: Paltani
- first_name: F.
full_name: Pasian, F.
last_name: Pasian
- first_name: K.
full_name: Pedersen, K.
last_name: Pedersen
- first_name: W. J.
full_name: Percival, W. J.
last_name: Percival
- first_name: V.
full_name: Pettorino, V.
last_name: Pettorino
- first_name: S.
full_name: Pires, S.
last_name: Pires
- first_name: G.
full_name: Polenta, G.
last_name: Polenta
- first_name: M.
full_name: Poncet, M.
last_name: Poncet
- first_name: L. A.
full_name: Popa, L. A.
last_name: Popa
- first_name: F.
full_name: Raison, F.
last_name: Raison
- first_name: A.
full_name: Renzi, A.
last_name: Renzi
- first_name: J.
full_name: Rhodes, J.
last_name: Rhodes
- first_name: G.
full_name: Riccio, G.
last_name: Riccio
- first_name: E.
full_name: Romelli, E.
last_name: Romelli
- first_name: M.
full_name: Roncarelli, M.
last_name: Roncarelli
- first_name: R.
full_name: Saglia, R.
last_name: Saglia
- first_name: Z.
full_name: Sakr, Z.
last_name: Sakr
- first_name: D.
full_name: Sapone, D.
last_name: Sapone
- first_name: B.
full_name: Sartoris, B.
last_name: Sartoris
- first_name: P.
full_name: Schneider, P.
last_name: Schneider
- first_name: T.
full_name: Schrabback, T.
last_name: Schrabback
- first_name: A.
full_name: Secroun, A.
last_name: Secroun
- first_name: G.
full_name: Seidel, G.
last_name: Seidel
- first_name: S.
full_name: Serrano, S.
last_name: Serrano
- first_name: P.
full_name: Simon, P.
last_name: Simon
- first_name: C.
full_name: Sirignano, C.
last_name: Sirignano
- first_name: G.
full_name: Sirri, G.
last_name: Sirri
- first_name: J.
full_name: Skottfelt, J.
last_name: Skottfelt
- first_name: L.
full_name: Stanco, L.
last_name: Stanco
- first_name: J.
full_name: Steinwagner, J.
last_name: Steinwagner
- first_name: P.
full_name: Tallada-Crespí, P.
last_name: Tallada-Crespí
- first_name: A. N.
full_name: Taylor, A. N.
last_name: Taylor
- first_name: H. I.
full_name: Teplitz, H. I.
last_name: Teplitz
- first_name: I.
full_name: Tereno, I.
last_name: Tereno
- first_name: N.
full_name: Tessore, N.
last_name: Tessore
- first_name: S.
full_name: Toft, S.
last_name: Toft
- first_name: R.
full_name: Toledo-Moreo, R.
last_name: Toledo-Moreo
- first_name: F.
full_name: Torradeflot, F.
last_name: Torradeflot
- first_name: I.
full_name: Tutusaus, I.
last_name: Tutusaus
- first_name: L.
full_name: Valenziano, L.
last_name: Valenziano
- first_name: J.
full_name: Valiviita, J.
last_name: Valiviita
- first_name: T.
full_name: Vassallo, T.
last_name: Vassallo
- first_name: G.
full_name: Verdoes Kleijn, G.
last_name: Verdoes Kleijn
- first_name: A.
full_name: Veropalumbo, A.
last_name: Veropalumbo
- first_name: Y.
full_name: Wang, Y.
last_name: Wang
- first_name: J.
full_name: Weller, J.
last_name: Weller
- first_name: A.
full_name: Zacchei, A.
last_name: Zacchei
- first_name: G.
full_name: Zamorani, G.
last_name: Zamorani
- first_name: I. A.
full_name: Zinchenko, I. A.
last_name: Zinchenko
- first_name: E.
full_name: Zucca, E.
last_name: Zucca
- first_name: V.
full_name: Allevato, V.
last_name: Allevato
- first_name: M.
full_name: Ballardini, M.
last_name: Ballardini
- first_name: E.
full_name: Bozzo, E.
last_name: Bozzo
- first_name: C.
full_name: Burigana, C.
last_name: Burigana
- first_name: R.
full_name: Cabanac, R.
last_name: Cabanac
- first_name: M.
full_name: Calabrese, M.
last_name: Calabrese
- first_name: A.
full_name: Cappi, A.
last_name: Cappi
- first_name: D.
full_name: Di Ferdinando, D.
last_name: Di Ferdinando
- first_name: J. A.
full_name: Escartin Vigo, J. A.
last_name: Escartin Vigo
- first_name: W. G.
full_name: Hartley, W. G.
last_name: Hartley
- first_name: M.
full_name: Huertas-Company, M.
last_name: Huertas-Company
- first_name: J.
full_name: Martín-Fleitas, J.
last_name: Martín-Fleitas
- first_name: S.
full_name: Matthew, S.
last_name: Matthew
- first_name: N.
full_name: Mauri, N.
last_name: Mauri
- first_name: R. B.
full_name: Metcalf, R. B.
last_name: Metcalf
- first_name: A.
full_name: Pezzotta, A.
last_name: Pezzotta
- first_name: M.
full_name: Pöntinen, M.
last_name: Pöntinen
- first_name: I.
full_name: Risso, I.
last_name: Risso
- first_name: V.
full_name: Scottez, V.
last_name: Scottez
- first_name: M.
full_name: Sereno, M.
last_name: Sereno
- first_name: M.
full_name: Tenti, M.
last_name: Tenti
- first_name: M.
full_name: Viel, M.
last_name: Viel
- first_name: M.
full_name: Wiesmann, M.
last_name: Wiesmann
- first_name: Y.
full_name: Akrami, Y.
last_name: Akrami
- first_name: I. T.
full_name: Andika, I. T.
last_name: Andika
- first_name: S.
full_name: Anselmi, S.
last_name: Anselmi
- first_name: M.
full_name: Archidiacono, M.
last_name: Archidiacono
- first_name: F.
full_name: Atrio-Barandela, F.
last_name: Atrio-Barandela
- first_name: D.
full_name: Bertacca, D.
last_name: Bertacca
- first_name: M.
full_name: Bethermin, M.
last_name: Bethermin
- first_name: L.
full_name: Bisigello, L.
last_name: Bisigello
- first_name: A.
full_name: Blanchard, A.
last_name: Blanchard
- first_name: L.
full_name: Blot, L.
last_name: Blot
- first_name: H.
full_name: Böhringer, H.
last_name: Böhringer
- first_name: M.
full_name: Bonici, M.
last_name: Bonici
- first_name: S.
full_name: Borgani, S.
last_name: Borgani
- first_name: M. L.
full_name: Brown, M. L.
last_name: Brown
- first_name: S.
full_name: Bruton, S.
last_name: Bruton
- first_name: A.
full_name: Calabro, A.
last_name: Calabro
- first_name: B.
full_name: Camacho Quevedo, B.
last_name: Camacho Quevedo
- first_name: F.
full_name: Caro, F.
last_name: Caro
- first_name: C. S.
full_name: Carvalho, C. S.
last_name: Carvalho
- first_name: T.
full_name: Castro, T.
last_name: Castro
- first_name: F.
full_name: Cogato, F.
last_name: Cogato
- first_name: S.
full_name: Conseil, S.
last_name: Conseil
- first_name: T.
full_name: Contini, T.
last_name: Contini
- first_name: A. R.
full_name: Cooray, A. R.
last_name: Cooray
- first_name: O.
full_name: Cucciati, O.
last_name: Cucciati
- first_name: G.
full_name: Desprez, G.
last_name: Desprez
- first_name: A.
full_name: Díaz-Sánchez, A.
last_name: Díaz-Sánchez
- first_name: S.
full_name: Di Domizio, S.
last_name: Di Domizio
- first_name: J. M.
full_name: Diego, J. M.
last_name: Diego
- first_name: P.
full_name: Dimauro, P.
last_name: Dimauro
- first_name: P. A.
full_name: Duc, P. A.
last_name: Duc
- first_name: M. Y.
full_name: Elkhashab, M. Y.
last_name: Elkhashab
- first_name: Y.
full_name: Fang, Y.
last_name: Fang
- first_name: A.
full_name: Finoguenov, A.
last_name: Finoguenov
- first_name: A.
full_name: Fontana, A.
last_name: Fontana
- first_name: F.
full_name: Fontanot, F.
last_name: Fontanot
- first_name: A.
full_name: Franco, A.
last_name: Franco
- first_name: K.
full_name: Ganga, K.
last_name: Ganga
- first_name: J.
full_name: García-Bellido, J.
last_name: García-Bellido
- first_name: T.
full_name: Gasparetto, T.
last_name: Gasparetto
- first_name: V.
full_name: Gautard, V.
last_name: Gautard
- first_name: R.
full_name: Gavazzi, R.
last_name: Gavazzi
- first_name: E.
full_name: Gaztanaga, E.
last_name: Gaztanaga
- first_name: F.
full_name: Giacomini, F.
last_name: Giacomini
- first_name: F.
full_name: Gianotti, F.
last_name: Gianotti
- first_name: A. H.
full_name: Gonzalez, A. H.
last_name: Gonzalez
- first_name: G.
full_name: Gozaliasl, G.
last_name: Gozaliasl
- first_name: M.
full_name: Guidi, M.
last_name: Guidi
- first_name: C. M.
full_name: Gutierrez, C. M.
last_name: Gutierrez
- first_name: A.
full_name: Hall, A.
last_name: Hall
- first_name: S.
full_name: Hemmati, S.
last_name: Hemmati
- first_name: H.
full_name: Hildebrandt, H.
last_name: Hildebrandt
- first_name: J.
full_name: Hjorth, J.
last_name: Hjorth
- first_name: J. J.E.
full_name: Kajava, J. J.E.
last_name: Kajava
- first_name: Y.
full_name: Kang, Y.
last_name: Kang
- first_name: V.
full_name: Kansal, V.
last_name: Kansal
- first_name: D.
full_name: Karagiannis, D.
last_name: Karagiannis
- first_name: K.
full_name: Kiiveri, K.
last_name: Kiiveri
- first_name: J.
full_name: Kim, J.
last_name: Kim
- first_name: C. C.
full_name: Kirkpatrick, C. C.
last_name: Kirkpatrick
- first_name: S.
full_name: Kruk, S.
last_name: Kruk
- first_name: L.
full_name: Legrand, L.
last_name: Legrand
- first_name: M.
full_name: Lembo, M.
last_name: Lembo
- first_name: F.
full_name: Lepori, F.
last_name: Lepori
- first_name: G.
full_name: Leroy, G.
last_name: Leroy
- first_name: G. F.
full_name: Lesci, G. F.
last_name: Lesci
- first_name: J.
full_name: Lesgourgues, J.
last_name: Lesgourgues
- first_name: L.
full_name: Leuzzi, L.
last_name: Leuzzi
- first_name: T. I.
full_name: Liaudat, T. I.
last_name: Liaudat
- first_name: A.
full_name: Loureiro, A.
last_name: Loureiro
- first_name: J.
full_name: Macias-Perez, J.
last_name: Macias-Perez
- first_name: E. A.
full_name: Magnier, E. A.
last_name: Magnier
- first_name: F.
full_name: Mannucci, F.
last_name: Mannucci
- first_name: R.
full_name: Maoli, R.
last_name: Maoli
- first_name: C. J.A.P.
full_name: Martins, C. J.A.P.
last_name: Martins
- first_name: L.
full_name: Maurin, L.
last_name: Maurin
- first_name: M.
full_name: Miluzio, M.
last_name: Miluzio
- first_name: P.
full_name: Monaco, P.
last_name: Monaco
- first_name: C.
full_name: Moretti, C.
last_name: Moretti
- first_name: G.
full_name: Morgante, G.
last_name: Morgante
- first_name: K.
full_name: Naidoo, K.
last_name: Naidoo
- first_name: A.
full_name: Navarro-Alsina, A.
last_name: Navarro-Alsina
- first_name: S.
full_name: Nesseris, S.
last_name: Nesseris
- first_name: D.
full_name: Paoletti, D.
last_name: Paoletti
- first_name: F.
full_name: Passalacqua, F.
last_name: Passalacqua
- first_name: K.
full_name: Paterson, K.
last_name: Paterson
- first_name: L.
full_name: Patrizii, L.
last_name: Patrizii
- first_name: A.
full_name: Pisani, A.
last_name: Pisani
- first_name: D.
full_name: Potter, D.
last_name: Potter
- first_name: M.
full_name: Radovich, M.
last_name: Radovich
- first_name: G.
full_name: Rodighiero, G.
last_name: Rodighiero
- first_name: S.
full_name: Sacquegna, S.
last_name: Sacquegna
- first_name: M.
full_name: Sahlén, M.
last_name: Sahlén
- first_name: D. B.
full_name: Sanders, D. B.
last_name: Sanders
- first_name: E.
full_name: Sarpa, E.
last_name: Sarpa
- first_name: C.
full_name: Scarlata, C.
last_name: Scarlata
- first_name: A.
full_name: Schneider, A.
last_name: Schneider
- first_name: M.
full_name: Schultheis, M.
last_name: Schultheis
- first_name: D.
full_name: Sciotti, D.
last_name: Sciotti
- first_name: E.
full_name: Sellentin, E.
last_name: Sellentin
- first_name: L. C.
full_name: Smith, L. C.
last_name: Smith
- first_name: S. A.
full_name: Stanford, S. A.
last_name: Stanford
- first_name: K.
full_name: Tanidis, K.
last_name: Tanidis
- first_name: G.
full_name: Testera, G.
last_name: Testera
- first_name: R.
full_name: Teyssier, R.
last_name: Teyssier
- first_name: S.
full_name: Tosi, S.
last_name: Tosi
- first_name: A.
full_name: Troja, A.
last_name: Troja
- first_name: M.
full_name: Tucci, M.
last_name: Tucci
- first_name: C.
full_name: Valieri, C.
last_name: Valieri
- first_name: A.
full_name: Venhola, A.
last_name: Venhola
- first_name: D.
full_name: Vergani, D.
last_name: Vergani
- first_name: G.
full_name: Verza, G.
last_name: Verza
- first_name: P.
full_name: Vielzeuf, P.
last_name: Vielzeuf
- first_name: N. A.
full_name: Walton, N. A.
last_name: Walton
citation:
ama: 'Gentile F, Daddi E, Elbaz D, et al. Euclid Quick Data Release (Q1): XII. Quenching
precedes bulge formation in dense environments but follows it in the field. Astronomy
and Astrophysics. 2026;711. doi:10.1051/0004-6361/202557633'
apa: 'Gentile, F., Daddi, E., Elbaz, D., Enia, A., Magnelli, B., Billand, J. B.,
… Walton, N. A. (2026). Euclid Quick Data Release (Q1): XII. Quenching precedes
bulge formation in dense environments but follows it in the field. Astronomy
and Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/202557633'
chicago: 'Gentile, F., E. Daddi, D. Elbaz, A. Enia, B. Magnelli, J. B. Billand,
P. Corcho-Caballero, et al. “Euclid Quick Data Release (Q1): XII. Quenching Precedes
Bulge Formation in Dense Environments but Follows It in the Field.” Astronomy
and Astrophysics. EDP Sciences, 2026. https://doi.org/10.1051/0004-6361/202557633.'
ieee: 'F. Gentile et al., “Euclid Quick Data Release (Q1): XII. Quenching
precedes bulge formation in dense environments but follows it in the field,” Astronomy
and Astrophysics, vol. 711. EDP Sciences, 2026.'
ista: 'Gentile F et al. 2026. Euclid Quick Data Release (Q1): XII. Quenching precedes
bulge formation in dense environments but follows it in the field. Astronomy and
Astrophysics. 711, A12.'
mla: 'Gentile, F., et al. “Euclid Quick Data Release (Q1): XII. Quenching Precedes
Bulge Formation in Dense Environments but Follows It in the Field.” Astronomy
and Astrophysics, vol. 711, A12, EDP Sciences, 2026, doi:10.1051/0004-6361/202557633.'
short: F. Gentile, E. Daddi, D. Elbaz, A. Enia, B. Magnelli, J.B. Billand, P. Corcho-Caballero,
C. Cleland, G. De Lucia, C. D’Eugenio, M. Fossati, M. Franco, C. Lobo, Y. Lyu,
M. Magliocchetti, G.A. Mamon, L. Quilley, J.G. Sorce, M. Tarrasse, M. Bolzonella,
F. Durret, L. Gabarra, S. Guo, L. Pozzetti, S. Quai, F. Shankar, V. Sangalli,
M. Talia, M. Baes, H. Fu, M. Girardi, J.J. Matthee, P.A. Oesch, D. Roberts, J.
Schaye, D. Scott, L. Spinoglio, B. Altieri, A. Amara, S. Andreon, N. Auricchio,
C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, R. Bender, A. Biviano, E.
Branchini, M. Brescia, J. Brinchmann, S. Camera, G. Cañas-Herrera, V. Capobianco,
C. Carbone, J. Carretero, S. Casas, M. Castellano, G. Castignani, S. Cavuoti,
K.C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, L. Conversi, Y. Copin,
F. Courbin, H.M. Courtois, M. Cropper, A. Da Silva, H. Degaudenzi, C. Dolding,
H. Dole, F. Dubath, C.A.J. Duncan, X. Dupac, S. Dusini, S. Escoffier, M. Fabricius,
M. Farina, R. Farinelli, S. Ferriol, F. Finelli, N. Fourmanoit, M. Frailis, E.
Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio,
A. Grazian, F. Grupp, S. Gwyn, S.V.H. Haugan, J. Hoar, W. Holmes, I.M. Hook, F.
Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, E. Keihänen, S. Kermiche,
A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A.M.C. Le Brun, S.
Ligori, P.B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano,
O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R.J. Massey,
E. Medinaceli, S. Mei, M. Melchior, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan,
A. Mora, M. Moresco, L. Moscardini, R. Nakajima, S.M. Niemi, C. Padilla, S. Paltani,
F. Pasian, K. Pedersen, W.J. Percival, V. Pettorino, S. Pires, G. Polenta, M.
Poncet, L.A. Popa, F. Raison, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli,
R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, A. Secroun,
G. Seidel, S. Serrano, P. Simon, C. Sirignano, G. Sirri, J. Skottfelt, L. Stanco,
J. Steinwagner, P. Tallada-Crespí, A.N. Taylor, H.I. Teplitz, I. Tereno, N. Tessore,
S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita,
T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, A. Zacchei,
G. Zamorani, I.A. Zinchenko, E. Zucca, V. Allevato, M. Ballardini, E. Bozzo, C.
Burigana, R. Cabanac, M. Calabrese, A. Cappi, D. Di Ferdinando, J.A. Escartin
Vigo, W.G. Hartley, M. Huertas-Company, J. Martín-Fleitas, S. Matthew, N. Mauri,
R.B. Metcalf, A. Pezzotta, M. Pöntinen, I. Risso, V. Scottez, M. Sereno, M. Tenti,
M. Viel, M. Wiesmann, Y. Akrami, I.T. Andika, S. Anselmi, M. Archidiacono, F.
Atrio-Barandela, D. Bertacca, M. Bethermin, L. Bisigello, A. Blanchard, L. Blot,
H. Böhringer, M. Bonici, S. Borgani, M.L. Brown, S. Bruton, A. Calabro, B. Camacho
Quevedo, F. Caro, C.S. Carvalho, T. Castro, F. Cogato, S. Conseil, T. Contini,
A.R. Cooray, O. Cucciati, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J.M. Diego,
P. Dimauro, P.A. Duc, M.Y. Elkhashab, Y. Fang, A. Finoguenov, A. Fontana, F. Fontanot,
A. Franco, K. Ganga, J. García-Bellido, T. Gasparetto, V. Gautard, R. Gavazzi,
E. Gaztanaga, F. Giacomini, F. Gianotti, A.H. Gonzalez, G. Gozaliasl, M. Guidi,
C.M. Gutierrez, A. Hall, S. Hemmati, H. Hildebrandt, J. Hjorth, J.J.E. Kajava,
Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C.C. Kirkpatrick, S. Kruk,
L. Legrand, M. Lembo, F. Lepori, G. Leroy, G.F. Lesci, J. Lesgourgues, L. Leuzzi,
T.I. Liaudat, A. Loureiro, J. Macias-Perez, E.A. Magnier, F. Mannucci, R. Maoli,
C.J.A.P. Martins, L. Maurin, M. Miluzio, P. Monaco, C. Moretti, G. Morgante, K.
Naidoo, A. Navarro-Alsina, S. Nesseris, D. Paoletti, F. Passalacqua, K. Paterson,
L. Patrizii, A. Pisani, D. Potter, M. Radovich, G. Rodighiero, S. Sacquegna, M.
Sahlén, D.B. Sanders, E. Sarpa, C. Scarlata, A. Schneider, M. Schultheis, D. Sciotti,
E. Sellentin, L.C. Smith, S.A. Stanford, K. Tanidis, G. Testera, R. Teyssier,
S. Tosi, A. Troja, M. Tucci, C. Valieri, A. Venhola, D. Vergani, G. Verza, P.
Vielzeuf, N.A. Walton, Astronomy and Astrophysics 711 (2026).
das_tickbox: '1'
dataavailabilitystatement: 'This work has made use of the Euclid Quick Release Q1
data from the Euclid mission of the European Space Agency (ESA), 2025, https://doi.org/10.57780/esa-2853f3b.
This work has made use of CosmoHub, developed by PIC (maintained by IFAE and CIEMAT)
in collaboration with ICE-CSIC. CosmoHub received funding from the Spanish government
(MCIN/AEI/10.13039/501100011033), the EU NextGeneration/PRTR (PRTR-C17.I1), and
the Generalitat de Catalunya. Based on data from UNIONS, a scientific collaboration
using three Hawaii-based telescopes: CFHT, Pan-STARRS, and Subaru www.skysurvey.cc.
Based on data from the Dark Energy Camera (DECam) on the Blanco 4-m Telescope at
CTIO in Chile https://www.darkenergysurvey.org'
date_created: 2026-07-12T22:02:18Z
date_published: 2026-07-01T00:00:00Z
date_updated: 2026-07-13T08:43:41Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1051/0004-6361/202557633
external_id:
arxiv:
- '2511.02964'
file:
- access_level: open_access
checksum: 29c087abb97eed26d4aa2a19bbb46666
content_type: application/pdf
creator: dernst
date_created: 2026-07-13T08:42:10Z
date_updated: 2026-07-13T08:42:10Z
file_id: '22277'
file_name: 2026_AstronomyAstrophysics_Euclid.pdf
file_size: 3482066
relation: main_file
success: 1
file_date_updated: 2026-07-13T08:42:10Z
has_accepted_license: '1'
intvolume: ' 711'
keyword:
- 'galaxies: evolution'
- 'galaxies: interactions'
- 'galaxies: statistics'
language:
- iso: eng
month: '07'
oa: 1
oa_version: Published Version
publication: Astronomy and Astrophysics
publication_identifier:
eissn:
- 1432-0746
issn:
- 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
researchdata_availability: no
scopus_import: '1'
status: public
supplementarymaterial: no
title: 'Euclid Quick Data Release (Q1): XII. Quenching precedes bulge formation in
dense environments but follows it in the field'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 711
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
_id: '22263'
abstract:
- lang: eng
text: Recent studies at high redshift have revealed an enigmatic class of little
red dots (LRDs) with extreme Balmer breaks, stronger than in any stellar atmosphere.
However, it is unclear whether such objects exist at lower redshift, especially
given the low number of LRDs reported at z ≲ 2. Here, we report the discovery
of PAN-BH*-1, an LRD with an extreme Balmer break at z = 1.73, identified from
JWST/NIRCam pure-parallel imaging taken by the PANORAMIC survey, and confirmed
by deep VLT/X-Shooter spectroscopy. The rest-optical to near-infrared spectral
energy distribution of PAN-BH*-1 is consistent with a photospheric continuum with
effective temperature Teff ≈ 4800 K. The broad Hα emission line shows remarkably
deep absorption, stronger than previously measured in any LRD. The absorption
trough spans from −520 to +267 km s−1 with respect to the systemic redshift. The
presence of blue- and red-shifted absorption suggests complex dynamics of the
obscuring gas along the line of sight. We speculate that the absorption trough
can be produced by a thick wind launched from a thick, rotating photospheric disk,
the latter being the source of the red optical continuum. While the source is
unresolved in the rest-optical JWST data (reff < 47 pc), the rest-near-UV Hubble
Space Telescope imaging shows an extended morphology with (formular displayed)
kpc, which we interpret as a host galaxy with a stellar mass of ∼10^8 M⊙, in line
with the narrow Hα emission. The discovery of this object at cosmic noon highlights
the feasibility of systematic searches for extreme LRDs with wide-area facilities
such as Euclid and Roman.
acknowledgement: "IOP Science home\r\nThe Astrophysical Journal Letters\r\nThe American
Astronomical Society, find out more.\r\n\r\nThe following article isOpen access\r\nA
Black Hole Star at Cosmic Noon: Extreme Balmer Break, Photospheric Continuum, and
Broad Absorption by Thick Winds in a Little Red Dot at z = 1.7\r\nAlberto Torralba,
Jorryt Matthee, Andrea Weibel, Rohan P. Naidu, Yilun Ma, Aidan P. Cloonan, Aayush
Desai, Anna de Graaff, Jenny E. Greene, Christian Kragh JespersenShow full author
list\r\n\r\nPublished 2026 June 30 • © 2026. The Author(s). Published by the American
Astronomical Society.\r\nThe Astrophysical Journal Letters, Volume 1005, Number
2\r\nCitation Alberto Torralba et al 2026 ApJL 1005 L37\r\nDOI 10.3847/2041-8213/ae7bfd\r\n\r\nPDFOpens
in a new tab.ePub\r\nAuthors\r\nFigures\r\nTables\r\nReferences\r\nArticle data\r\nPDFOpens
in a new tab.ePub\r\nArticle metrics\r\n122 Total downloads\r\n\r\nShare this article\r\nArticle
information\r\nAbstract\r\nRecent studies at high redshift have revealed an enigmatic
class of little red dots (LRDs) with extreme Balmer breaks, stronger than in any
stellar atmosphere. However, it is unclear whether such objects exist at lower redshift,
especially given the low number of LRDs reported at z ≲ 2. Here, we report the discovery
of PAN-BH*-1, an LRD with an extreme Balmer break at z = 1.73, identified from JWST/NIRCam
pure-parallel imaging taken by the PANORAMIC survey, and confirmed by deep VLT/X-Shooter
spectroscopy. The rest-optical to near-infrared spectral energy distribution of
PAN-BH*-1 is consistent with a photospheric continuum with effective temperature
Teff ≈ 4800 K. The broad Hα emission line shows remarkably deep absorption, stronger
than previously measured in any LRD. The absorption trough spans from −520 to +267
km s−1 with respect to the systemic redshift. The presence of blue- and red-shifted
absorption suggests complex dynamics of the obscuring gas along the line of sight.
We speculate that the absorption trough can be produced by a thick wind launched
from a thick, rotating photospheric disk, the latter being the source of the red
optical continuum. While the source is unresolved in the rest-optical JWST data
(reff < 47 pc), the rest-near-UV Hubble Space Telescope imaging shows an extended
morphology with \r\n kpc, which we interpret as a host galaxy with a stellar mass
of ∼108 M⊙, in line with the narrow Hα emission. The discovery of this object at
cosmic noon highlights the feasibility of systematic searches for extreme LRDs with
wide-area facilities such as Euclid and Roman.\r\n\r\nExport citation and abstract\r\nBibTeXRIS\r\n\r\nPrevious
article in issue\r\nNext article in issue\r\n\r\nOriginal content from this work
may be used under the terms of the Creative Commons Attribution 4.0 licence. Any
further distribution of this work must maintain attribution to the author(s) and
the title of the work, journal citation and DOI.\r\n\r\n1. Introduction\r\nThe unprecedented
sensitivity of JWST has enabled the discovery of a new, abundant population of objects
at redshifts z ≈ 3–9 nicknamed the “little red dots” (LRDs). These are characterized
by their compact rest-frame optical morphology, broad emission lines, and a characteristic
rest-UV to optical “V-shape” in their spectral energy distributions (SED; e.g.,
D. D. Kocevski et al. 2023; V. Kokorev et al. 2024; J. Matthee et al. 2024; I. Labbe
et al. 2025).\r\n\r\nThe nature of LRDs is highly debated (see K. Inayoshi & L.
C. Ho 2025, for a recent overview) as the LRDs show systematic differences with
respect to other types of active galactic nuclei (AGN), such as faintness in X-rays
(e.g., T. T. Ananna et al. 2024; M. Yue et al. 2024), mid-to-far-infrared dust emission
(e.g., G. C. K. Leung et al. 2025; C. C. Williams et al. 2024; I. Delvecchio et
al. 2025; D. J. Setton et al. 2025; M. Xiao et al. 2025), and radio (e.g., G. Mazzolari
et al. 2026; M. A. Latif et al. 2025; K. Perger et al. 2025, see A. J. Gloudemans
et al. 2025).\r\n\r\nA recurring spectral feature of LRDs is the presence of a strong
Balmer break (e.g., D. J. Setton et al. 2025; B. Wang et al. 2024; R. E. Hviding
et al. 2025; W. Q. Sun et al. 2026), in some cases stronger than any star or stellar
population can produce. The two most prominent examples known to date are The Cliff
at z ≈ 3.5 (A. de Graaff et al. 2025a) and MoM-BH* at z ≈ 7.8 (R. P. Naidu et al.
2025). The joint appearance of strong Balmer lines as well as strong Balmer breaks
has been modeled as being due to absorption by a dense, neutral gas with a high
column density in the line of sight to a highly ionizing source (K. Inayoshi & R.
Maiolino 2025; X. Ji et al. 2025; A. Sneppen et al. 2026; A. Torralba et al. 2026).
These observations have sparked the development of new theoretical models, ranging
from a spherical envelope analogous to stellar atmospheres (e.g., M. C. Begelman
& J. Dexter 2026; D. Kido et al. 2025; H. Liu et al. 2025; D. Nandal & A. Loeb 2026)
or a thick accretion disk (e.g., H. Liu et al. 2025, 2026; K. Inayoshi et al. 2025;
Y.-X. Chen et al. 2026).\r\n\r\nBesides their spectral features, the evolution of
the LRD number densities is also in stark contrast to other types of AGNs (e.g.,
K. Inayoshi 2025). At 4 ≲ z ≲ 7, LRDs represent a few percent of the galaxy population
(e.g., D. D. Kocevski et al. 2023, 2025; J. E. Greene et al. 2024; V. Kokorev et
al. 2024; X. Lin et al. 2024; R. Maiolino et al. 2024; J. Matthee et al. 2024),
with number densities of ≳10−5 Mpc−3. The number density does not appear to drop
quickly beyond z > 5 (e.g., J. Zhang et al. 2026), with various LRDs having been
confirmed at z > 8 (V. Kokorev et al. 2023; A. J. Taylor et al. 2025; R. Tripodi
et al. 2025), well beyond the quasar redshift record (F. Wang et al. 2021). Photometric
LRD candidates exist beyond z > 10 (T. S. Tanaka et al. 2025). In turn, the number
density of LRDs seems to decline steeply at z < 4 (e.g., Y. Ma et al. 2026), with
estimates of a number density of ∼10−6 cMpc−3 at z ∼ 2 and even ∼10−10 cMpc−3 at
z ≈ 0.3 (X. Lin et al. 2026). While it is challenging to ensure a uniform selection
function across such a large redshift baseline and dedicated spectroscopic follow-up
of such lower redshift candidates has only just started, it is challenging to attribute
five orders of magnitude to such effects.\r\n\r\nMotivated by the discovery of rare
objects with extreme Balmer breaks at z > 3 and the very small number of known
LRDs at lower redshift, we performed a dedicated search for extreme Balmer break
objects using a template-match approach on a large compilation of JWST NIRCam data
over ≈0.3 deg2 and z ≈ 1.5–7.0. This survey is presented in A. Weibel et al. (2026a).
As part of an ongoing ground-based spectroscopic campaign of LRD candidates at z
∼ 2 (Y. Ma et al. 2026), we followed up the most luminous candidate with a photometric
redshift of z ≈ 2 with the X-Shooter spectrograph on the Very Large Telescope (VLT).
In this Letter, we present the discovery and spectroscopic confirmation of PAN-BH*-1,
a luminous LRD at z = 1.73 with an extreme Balmer break comparable to the strongest
observed in any LRD (and, in general, any astrophysical source). The low redshift
of this source enables high-resolution spectroscopy from ground-based observatories
that is otherwise impossible to obtain at high redshift.\r\n\r\nThroughout this
Letter, we use a ΛCDM cosmology with Ωm = 0.31, ΩΛ = 0.69, and h = 0.677 as described
by Planck Collaboration et al. (2020). All the magnitudes are given in the AB system
(J. B. Oke & J. E. Gunn 1983).\r\n\r\n2. Observations\r\n2.1. Photometry and Source
Selection\r\nWe identified PAN-BH*-1 (ID: PAN-1115, RA, DEC: 40.015835, −1.659363
J2000) as part of a systematic search across ≈0.3 deg2 of JWST NIRCam legacy imaging
comprising at least six filters of coverage (A. Weibel et al. 2026b). Notably, this
dataset includes the Cycle 1 pure parallel survey PANORAMIC (PID: 2514, PIs: Williams
& Oesch; C. C. Williams et al. 2025) that contributes 28 of the 35 independent lines
of sight, thereby enabling the discovery of rare objects such as PAN-BH*-1 across
diverse large-scale structure environments. Specifically, this source was identified
in the footprint j024000m0142 of the PANORAMIC DR1,15 which is adjacent to the A370
field (G. O. Abell et al. 1989), where archival images by the Hubble Space Telescope
(HST) are available from the BUFFALO survey (C. L. Steinhardt et al. 2020). The
HST/ACS images were processed with grizli and also released as part of the PANORAMIC
dataset.\r\n\r\nPAN-BH*-1 is in the outskirts of the A370 lensing cluster, but the
magnification is only μ ≈ 1.05 according to the models from A. Niemiec et al. (2023).
Throughout the rest of the paper, we report the uncorrected flux measurements, since
the effect of magnification (∼5%) is negligible given the uncertainties in the observations
and the lensing model.\r\n\r\nThe search strategy and full photometric selection
are described in a companion paper (A. Weibel et al. 2026a). Briefly, that work
presents a new selection of LRDs as a combination of a “black hole star” template
(BH*; R. P. Naidu et al. 2025) embedded in a host galaxy, instead of the typically
used “V-shaped” selections (e.g., D. D. Kocevski et al. 2025; V. Kokorev et al.
2024). The host galaxies are modeled using eazy’s blue_sfhz templates. The BH*s
are modeled using a novel template set comprising empirical luminosity-based stacks
constructed in W. Q. Sun et al. (2026), the cloudy template from R. P. Naidu et
al. (2025), and by using spectra of prominent LRDs spanning the observed effective
temperature range (I. Labbe et al. 2024; A. de Graaff et al. 2025a; B. Wang et al.
2026).\r\n\r\nPAN-BH*-1 stood out as one of the few sources where the BH* template
effectively dominated all the light over the full wavelength range covered by NIRCam
(hence the name). The redshift of PAN-BH*-1 was estimated to be zphot = 1.85. Follow-up
VLT/X-Shooter spectroscopy confirmed the redshift as zspec = 1.731 (see Section
3.2).\r\n\r\nPAN-BH*-1 is also covered by archival data from the VLT with the HAWK-I
camera in the Ks band (G. B. Brammer et al. 2016) and in data from the Spitzer Space
Telescope in IRAC bands 1 and 3 (3.6 and 5.7 μm), and MIPS 24 μm (P. Capak 2019).
PAN-BH*-1 is detected in the Ks band and in the two IRAC filters. Performing Spitzer
photometry of this source is challenging due to the large point spread function
(PSF) and a neighboring source, especially in the MIPS band. However, the NIRCam
photometry of the neighboring source suggests it has a limited contribution to the
IRAC fluxes. The details of the photometry extraction are described in Appendix
A, and the measured magnitudes in Table 2.\r\n\r\n2.2. VLT/X-Shooter Spectroscopy\r\nPAN-BH*-1
was observed for 5.8 ks with the X-Shooter spectrograph (J. Vernet et al. 2011)
on the VLT as a bright backup target for program 116.294D (PI: Matthee) in visitor
mode on 2025 December 17. The main aim of this program was to confirm candidate
LRDs at cosmic noon (Y. Ma et al. 2026). These observations confirmed the redshift
through the detection of Hα at z = 1.731. A DDT program (ID 116.2AQ0; PI: Matthee)
obtained additional follow-up data of PAN-BH*-1 in service mode for 26.2 ks during
2026 January 10–26, yielding a total exposure time of 8.9 hr. X-Shooter observes
with three arms simultaneously, UVB, VIS, and near-infrared (NIR), covering rest-frame
wavelengths of ≈0.14–0.9 μm, albeit hampered by skyline emission and telluric absorption,
primarily in the rest-frame optical.\r\n\r\nThe observing conditions were clear,
with a seeing ranging from 05 to 07 (median 06). The service mode observations were
primarily conducted during dark nights, with some gray (FLI = 0.03–0.6, median 0.1),
and a typical airmass of 1.35. We used UVB, VIS, and NIR slits with widths 10, 09,
and 09, yielding a nominal resolution of R = 5400, 8900, and 5600, respectively
(FWHM ∼53 km s−1 for NIR). The target acquisition was done using blind offsets from
a reference star, due to the target being too faint for direct acquisition. We used
a standard nodding on the slit pattern, with 4″ nod throws in an ABBA pattern, and
1″ jitters in the NIR arm to improve the sky subtraction. In each observing block
of ≈1 hr, the exposure times were 700, 655, and (2×)365 s for the three arms at
each nod position.\r\n\r\nThe reduction of the X-Shooter data uses a combination
of EsoRex libraries16 and Python code based on the reduction pipeline employed in
J. Matthee et al. (2021). Each observing block was reduced separately. We used standard
stars taken during the observing night for a first-pass flux calibration. Telluric
corrections were applied using the molecfit tool (A. Smette et al. 2015) implemented
in the X-Shooter EsoRex pipeline. Telluric stars were observed during the visitor
nights, but they were not always observed during the service mode observations in
January. For those observations, we took the telluric star that was observed at
the closest observing date. Based on the variation in telluric absorption among
the reference stars taken during this period, we estimate the variation in the transmission
and propagate the uncertainty in the telluric correction. For each observing block,
we then extracted an optimally extracted 1D spectrum using the spatial profile of
the Hα line, thus accounting for seeing variations and (more importantly) minor
errors in the accuracy of the slit pointing. Before median combining these spectra,
we normalize them by the median Hα flux of all observations to account for variations
in slit losses and flux calibrations.\r\n\r\nBesides Hα (integrated S/N = 75) and
Hβ (integrated S/N = 6; Section 3.2), we also detect continuum emission in the best
regions in the H and K bands at 1.6 μm and 2.1 μm, respectively, with a low signal-to-noise
ratio (S/N) of ∼1 per resolution element. Unfortunately, the [O iii] λλ4960, 5008
doublet is undetectable because the observed wavelengths are impacted by very strong
telluric absorption. No other lines or continuum are detected in the X-Shooter spectrum.\r\n\r\n3.
Properties of PAN-BH*-1\r\n3.1. Spectral Shape: A Photospheric Continuum with Strong
Hα Emission\r\nThe photometric SED of PAN-BH*-1 has remarkable similarities with
The Cliff (Figure 1): luminous in the rest optical, with a sudden drop toward the
rest-UV around the Balmer limit, and very weak near-to-mid infrared continuum emission.
With a rough extrapolation of the two HST photometric points using a power-law fit
(fλ ∝ λβ), we obtain a UV slope of β = −0.1 ± 1.2, and MUV = −16.7 ± 0.7. For the
rest-frame optical to NIR data, we fit a Planck blackbody law to the JWST data points,
after subtracting the measured Hα flux (see Section 3.2) from the F200W photometry.
The rest-optical and NIR photometry of PAN-BH*-1 is remarkably well described by
a single temperature blackbody with T = 4204 K (with a best-fit ). We measure the
strength of the Balmer break from the fν ratio F115W/F814W = 7 ± 1, in line with
the Balmer break strengths of The Cliff (; A. de Graaff et al. 2025a)17 and MoM-BH*
(7.8 ± 1.8; R. P. Naidu et al. 2025), measured from JWST/NIRSpec PRISM spectra as
fν,4000–4100/fν,3620−3720. In Figure 2, we compare the Balmer break strength with
the spectroscopic sample of A. de Graaff et al. (2025b), showing that out of 134
sources, only two have breaks significantly above 5. This suggests that PAN-BH*-1
has among the most extreme Balmer breaks known, although we caution that our value
is derived from wide-band photometry with pivot wavelengths corresponding to 4212
and 3042 Å, respectively, rather than from spectroscopy.\r\n\r\nZoom InZoom OutReset
image size\r\nFigure 1. SED of PAN-BH*-1 Top: cutouts from all the HST and JWST
images in which PAN-BH*-1 is covered. It shows a remarkably compact morphology in
all the wavelengths, resolved only in the HST F606W and F814W bands (Section 3.3).
Bottom: photometry from JWST/NIRCam (blue squares), HST/ACS (purple pentagons),
and Spitzer/IRAC+MIPS (red hexagons, and red triangle for the 5σ upper limit). The
empty square is the F200W flux after subtracting the Hα flux measured from X-Shooter
spectroscopy. We show the spectrum of The Cliff for comparison (gray line), shifted
to z = 1.73 and normalized to the F150W flux of PAN-BH*-1. We also show the best-fitting
blackbody spectrum (blue dashed line) and the best model from the synthetic LRD
atmosphere models from H. Liu et al. (2026), shifted to z = 1.73 (green line), undersampled
by a factor of 500 for clarity.\r\n\r\nDownload figure:\r\n\r\nStandard imageHigh-resolution
image\r\nZoom InZoom OutReset image size\r\nFigure 2. Spectroscopic sample of LRDs
by redshift and Balmer break strength. We plot the redshift and Balmer break strength
of PAN-BH*-1, and the JWST sample from A. de Graaff et al. (2025b) (purple diamonds),
and three local LRDs in X. Lin et al. (2026), for comparison. We also highlight
three sources with a particularly strong Balmer break: The Cliff (A. de Graaff et
al. 2025a), MoM-BH* (R. P. Naidu et al. 2025), and CAPERS-LRDz9 (A. J. Taylor et
al. 2025). The Balmer break strength of the JWST spectroscopic sample is computed
as fν,4000–4100/fν,3620–3720, whereas the value for PAN-BH*-1 is directly obtained
from the F115W/F814W photometry.\r\n\r\nDownload figure:\r\n\r\nStandard imageHigh-resolution
image\r\n3.2. Hα and Hβ Emission Lines\r\nThe Hα profile appears as a complex combination
of a broad line with strong absorption close to the systemic redshift. We fit the
Hα emission line with a similar model as the one used in A. Torralba et al. (2026)
and J. Matthee et al. (2026). The Hα model consists of two Gaussian emission components
(with narrow and intermediate line widths), and a broad symmetric exponential convolved
with the intermediate profile and parameterized as in F. D’Eugenio et al. (2025a).
The absorption is implemented as an opacity law defined as e−τ(λ), where τ(λ) also
follows a single Gaussian velocity distribution (F. D’Eugenio et al. 2025a, 2025b;
A. Torralba et al. 2026). For simplicity, we assume a covering factor of Cf = 1
for the absorbing gas. In previous works, the width of the narrow component is tied
to that of [O iii], assuming both components come from the same region, often interpreted
as the interstellar medium (ISM) of the host galaxy. In this case, we have no information
about [O iii] due to this doublet falling in a wavelength range heavily affected
by strong telluric absorption. We fit the Hα line after masking relevant skylines
and strong telluric absorption bands. The fitted Hα parameters are listed in Table
1 and the best-fit model is shown in Figure 3. The absorption feature is notably
strong, with an equivalent width of EWabs = −148 ± 12 Å with respect to the fitted
continuum and 12.2 ± 0.2 Å if including the broad emission component. The absorption
corresponds to a Balmer optical depth at the line center of , reaching roughly the
continuum level. The FWHM of the single Gaussian fitted to the absorber is 283 ±
\ 8 km s−1, and is offset from the systemic redshift by −94 ± 4 km s−1. We note
that this parameterization is somewhat arbitrary, and we discuss in detail the absorber
properties in Section 4.\r\n\r\nZoom InZoom OutReset image size\r\nFigure 3. Hα
spectrum, and the best fit to our fiducial model. We show the X-Shooter R ∼ 5600
spectrum of the Hα line of PAN-BH*-1, along with the best-fit to the model described
in Section 3.2; total model (red solid line) and individual components (discontinuous
color lines). The red wing of the line is severely affected by telluric absorption,
thus the large uncertainties.\r\n\r\nDownload figure:\r\n\r\nStandard imageHigh-resolution
image\r\nTable 1. Properties of PAN-BH*-1\r\n\r\nParameter\tValue\tUnit\r\nWidth
(FWHM; Hα)\r\nExponential\t1257 ± 27\tkm s−1\r\nIntermediate\t687 ± 43\tkm s−1\r\nNarrow\t184
± 12\tkm s−1\r\nAbsorption\t283 ± 8\tkm s−1\r\nFlux (Hα)\r\nExponential\t643 ± 7\t10−18
erg s−1 cm−2\r\nIntermediate\t19 ± 5\t10−18 erg s−1 cm−2\r\nNarrow\t38 ± 3\t10−18
erg s−1 cm−2\r\nTotal\t522 ± 7\t10−18 erg s−1 cm−2\r\nGeneral properties\r\n(LHα/erg
s−1)\t43.046 ± 0.006\t⋯\r\nEW0(Hα)\t520 ± 20\tÅ\r\nSFR(Hα, narrow)a\t2.1 ± 0.2\tM⊙
yr−1\r\nSFR(Hα, narrow)b\t3.3 ± 0.3\tM⊙ yr−1\r\nreff,UV (F606W+F814W)\t\tkpc\r\nreff,opt
(F200W)\t<0.047\tkpc\r\nHα/Hβ (total)\t>9.4\t⋯\r\nHα/Hβ (narrow)\t5 ± 1\t⋯\r\nNotes.
aCalibration from I. G. Kramarenko et al. (2026). bCalibration from R. C. Kennicutt
& N. J. Evans (2012). SFR values calculated assuming no dust attenuation.\r\n\r\nDownload
table as: \r\nASCIITypeset image\r\n\r\nThe Hβ line is marginally detected. After
undersampling the spectrum by a factor 5, a hint of a weak narrow component can
be identified (Figure 4), along with a tentative absorption at the same mean velocity
as in Hα. We fit the best Hα model to the Hβ spectrum, only rescaling it by a multiplicative
factor, and adding a flat continuum component. By doing this, we find an Hβ flux
of (47 ± 8) × 10−18 erg s−1 cm−2 (S/N ≈ 6). Conservatively, we obtain a Balmer decrement
of Hα/Hβ > 9.4 (at a 3σ confidence level), in line with the high decrements found
for the LRD population (e.g., G. P. Nikopoulos et al. 2026; A. de Graaff et al.
2025b; J. Matthee et al. 2026). In Figure 5, we show the Hβ spectrum compared to
the rescaled Hα model. By matching the best-fit Hα profile with the data at the
expected observed wavelength for Hβ (±5000 km s−1), we obtain a better agreement
(, BIC = 1537) than fitting a flat continuum only (, BIC = 1658) with ΔBIC = 121
≫ 10, strongly favoring a detection of a broad Hβ emission line, and securing the
spectroscopic redshift. Similarly, we fit a narrow Gaussian to Hβ with the same
width and velocity as the Hα best-fit model, assuming a completely saturated absorption.
We obtain a Balmer decrement for the narrow component of Hα/Hβ = 5 ± 1, which would
imply a dust extinction of using a J. A. Cardelli et al. (1989) attenuation law,
under the assumption of case B recombination. However, due to the low S/N of Hβ
this result is only tentative, and compatible with a standard Case B value within
∼2σ.\r\n\r\nZoom InZoom OutReset image size\r\nFigure 4. X-Shooter spectrum of Hα
and Hβ of PAN-BH*-1 (blue). We compare to the spectrum of The Cliff (gray; data
from JWST DDT #9433), normalized in each panel to the flux of PAN-BH*-1 in the range
v ∈ (−3000, −2000) km s−1. Due to the low S/N, the Hβ spectrum of PAN-BH*-1 is rebinned
to a coarser grid by a factor 5, after masking the most relevant skylines.\r\n\r\nDownload
figure:\r\n\r\nStandard imageHigh-resolution image\r\nZoom InZoom OutReset image
size\r\nFigure 5. Hβ spectrum. The spectrum is rebinned by a factor of 10 with inverse
variance flux weighting for visual clarity, due to the low S/N. We compare to the
best-fit Hα model, scaled by a factor of 0.112. In the bottom panel, we show the
χ residuals between the spectrum and the rescaled Hα model in black, and for only
the continuum in pink (ΔBIC = 121 strongly favoring the presence of a broad Hβ line).\r\n\r\nDownload
figure:\r\n\r\nStandard imageHigh-resolution image\r\n3.3. Spatial Morphology\r\nIn
order to assess whether PAN-BH*-1 is spatially resolved, we use the Bayesian profile
fitting software pysersic (I. Pasha & T. B. Miller 2023)18 to fit a single Sérsic
profile to the JWST and HST imaging data of PAN-BH*-1. For JWST/NIRCam, we choose
F200W as the filter with the highest S/N in the short wavelength channel, benefiting
from a high spatial resolution and probing rest-frame optical wavelengths. To model
its PSF, we use version 2.2.0 of the stpsf software (formerly webbpsf, M. D. Perrin
et al. 2014). For the two HST bands F606W and F814W, we instead construct empirical
PSFs from public imaging data in the GOODS-S field following A. Weibel et al. (2024).
In all three bands, we sample the posterior with the No U-turn sampler in two chains
with 1000 warm-up and 2000 sampling steps each. We find that PAN-BH*-1 is unresolved
with NIRCam in F200W where the effective radius converges toward the edge of the
prior at 0.25 pixels. Using the 95th percentile of the posterior chains as an upper
limit on the effective radius, we find a rest-optical size of reff < 47 pc.\r\n\r\nPAN-BH*-1
appears to be resolved in the HST images corresponding to rest-frame pivot 0.2 and
0.3 μm, respectively. Due to the low signal-to-noise of the F606W and F814W photometry,
we fit both bands simultaneously fixing all the morphological parameters in both
images. We measure physical effective radii of kpc (see Appendix B). The modest
stretching by the foreground A370 lensing cluster could imply a correction of ∼10%
to the measured radius (A. Niemiec et al. 2023), which we disregard given the uncertainties.
These measured sizes are consistent with the typical sizes for galaxies with a stellar
mass ≲ 109 M⊙ at z = 1.75 (A. van der Wel et al. 2014). These findings are consistent
with the scenario of a compact LRD “engine” dominating the rest-optical light embedded
in a host galaxy, whose contribution becomes significant blueward of the Balmer
break (see A. P. Cloonan et al. 2026, for a relevant discussion).\r\n\r\n4. Absorber
Kinematics\r\nAs described in Section 3.2, the velocity distribution of the absorber
is empirically modeled with a Gaussian, which we find has a central velocity of
−94 ± 4 km s−1 relative to the redshift of the narrow emission component (adopted
as systemic). The absorption trough extends from negative to positive velocities
with respect to the redshift of the narrow component, but also with respect to the
center of the symmetric exponential wings. However, there are several degeneracies
between the shape of the absorber and other components of the emission line, such
as the narrow central emission (see Section 3.2). Furthermore, direct interpretation
of the absorber center velocity shift is challenging in an optically thick gas with
presumably complex dynamics, and it does not necessarily trace bulk motion. A more
robust, physically motivated pair of quantities is the minimum and maximum absorber
velocities. We define them as the values where the transmission of the Balmer absorber
increases to 99%, km s−1 and km s−1. These values trace the largest velocities
in the line of sight of gas with significant Balmer absorption. The absorbing trough
extends over 787 ± 17 km s−1 under this definition. The values of and are relatively
agnostic to the choice of the shape of the absorber, since they are determined by
the wavelength where the line profile deviates from a broad, symmetric exponential
profile. In Figure 6, we illustrate three proposed configurations of the velocity
distribution of the absorbing gas that could explain the shape of the observed Balmer
absorption, and we discuss these scenarios below.\r\n\r\nZoom InZoom OutReset image
size\r\nFigure 6. Geometric configurations for the absorber. We illustrate three
scenarios that could give rise to the observed Balmer absorption in PAN-BH*-1. In
scenario (a), the obscuring agent is a thick screen of gas with a certain bulk velocity,
and turbulent motions produce the broadening of the absorption trough. In (b), there
are two (or more) absorbers with opposite velocities in the line of sight. These
first two scenarios are dynamically unstable; therefore, variability is expected
in the absorption. Lastly, in (c), we observed an extended source through a disk
wind with a rotational component (vϕ) in addition to the poloidal (nonazimuthal)
velocity (vp). In the last scenario, the redshifted absorption is produced by streamlines
that oppose the observer when projected along the line of sight, despite the fact
that the gas is outflowing from the central source.\r\n\r\nDownload figure:\r\n\r\nStandard
imageHigh-resolution image\r\n4.1. Unstable Gas Flows?\r\nThe fact that there is
significant absorption at both negative and positive velocities with respect to
the systemic redshift cannot be simply explained by an axisymmetric outflowing or
inflowing wind. In the case of observing a compact object through a spherically
symmetric, nonturbulent bulk flow, a classical P Cygni profile is expected, with
a purely blueshifted absorption (or redshifted if the wind is infalling). The fact
that we also see redshifted absorption rules out this simple scenario. In principle,
turbulent motions could also produce broadening of the absorbing medium (scenario
a in Figure 6). However, the required turbulent velocity dispersion σturb ≈ 120
km s−1 (from the Gaussian fit in Section 3.2) is comparable to the mean velocity
of the absorption trough, meaning that turbulence dominates the gas flow. In such
a case, strong variability of the absorption profile would be expected, given the
typical dynamical crossing times (see Sect. 4.1 in F. D’Eugenio et al. 2025b). For
example, for a radius of 1016 cm (e.g., A. Torralba et al. 2026) and a mass of 106
M⊙, the dynamical freefall time is yr. Moreover, the turbulent velocity would be
highly supersonic, and the dissipation timescale would be comparable to the dynamical
time (e.g., M.-M. Mac Low 1999). Alternatively, in the context of a strong Balmer
absorber at z ∼ 7, F. D’Eugenio et al. (2026) recently discussed a “breathing mode”
scenario with cyclic inflows and outflows along the same line of sight, with the
gas being in different phases at different depths (scenario b in Figure 6; see also
K. Park et al. 2017). In this case, the same arguments regarding the stability of
the absorber would apply, and absorber variability is expected on observed timescales
of ∼5 yr (for a source at z = 1.7), which is testable with future observations.\r\n\r\n4.2.
The Case for the Disk Wind Hypothesis\r\nAn alternative, dynamically stable scenario
is a disk wind configuration (scenario c in Figure 6). Here, the wind would be launched
from a thick disk near the central engine, which we speculate could be the source
of the optical continuum emission (e.g., H. Liu et al. 2025, 2026; L. Zwick et al.
2025; Y.-X. Chen et al. 2026). A rotating disk would imprint to the wind an azimuthal
velocity component (vϕ). Observations at specific lines of sight, particularly for
high inclination angles (close to edge-on) where the rotational component dominates
the poloidal velocity, can give rise to both blueshifted and redshifted absorption
features (D. Proga et al. 2000; P. B. Hall et al. 2002, 2013; D. Proga & T. R. Kallman
2004; M. Giustini & D. Proga 2012). Most observed LRDs have blueshifted P Cygni–like
absorbers (J. Matthee et al. 2026), which can be naively interpreted as a uniformly
expanding shell. The low incidence of redshifted Balmer absorbers in LRD spectra
(e.g., I. Labbe et al. 2024; A. de Graaff et al. 2025a; F. D’Eugenio et al. 2025b,
2026; Y. Ma et al. 2026) can therefore be explained by the requirement of high inclination
angles to observe such features (see also A. Sneppen et al. 2026). Such a picture
is broadly in line with disk wind models for AGN with broad absorption lines (e.g.,
P. B. Hall et al. 2002; H. Zhou et al. 2019) and around stars with circumstellar
disks (e.g., J. Erkal et al. 2022), such as accreting T Tauri stars (S. Edwards
et al. 2006) or cataclysmic variables (D. Proga 2003).\r\n\r\n4.3. Implications
of Rotating Winds for the Emission Lines of LRDs\r\nThe disk wind hypothesis would
imply that a photosphere in the shape of a rotating disk is the source of the optical
continuum emission, and drives winds that can explain the observed absorption trough.
Emission lines originating in a thin rotating disk would have a double-peaked profile
in the idealized case (for most inclination angles), but this is not necessarily
true if the disk is not sufficiently thin (e.g., N. Murray & J. Chiang 1997), for
instance, in the case of a puffed-up disk associated with super-Eddington accretion
(e.g., H. Liu et al. 2026). In addition, most line emission would not be produced
directly at the base of the disk, but slightly outside (e.g., via collisional cooling
or residual recombination; A. Torralba et al. 2026), where the rotational velocity
is lower, and the dynamics are complex (e.g., G. A. Shields 1977).\r\n\r\nThe Balmer
lines of most LRDs are dominated by broad, symmetric exponential components that
are associated with broadening by electron scattering (e.g., V. Rusakov et al. 2026;
J. Matthee et al. 2026). For PAN-BH*-1, the Hα line profile of PAN-BH*-1 is compatible
with a broad exponential profile emerging through a dense wind where the absorption
trough is produced. In dense gas with a large column density of neutral hydrogen,
and optically thick to Balmer transitions (NHI,2s ≳ 1014 cm−2), resonant scattering
effects become important. Crucially, resonant scattering impacts Hα and Hβ differently
(e.g., S.-J. Chang et al. 2026), hence the 3D radiative transfer and photon redistribution
of both lines may produce different profiles (see, e.g., Figure 2 in D. Proga 2003).
Therefore, the empirical fitting and interpretation of the absorption profiles becomes
nontrivial. Dedicated radiative transfer modeling is necessary to study such effects,
and they can be tested in other emission lines with high optical depth, such as
He i λ10830 Å, or resonant lines like C iv λ1550.\r\n\r\n5. Implications for the
Galaxy and Black Hole Masses\r\n5.1. Properties of the Host Galaxy\r\nAssuming that
the narrow component of Hα corresponds to ISM emission in the host galaxy, we compute
the associated star formation rate using the local calibration from R. C. Kennicutt
& N. J. Evans (2012) and assuming no dust attenuation. We obtain SFR(Hα) = 3.3 ±
0.3 M⊙ yr−1. A somewhat lower value of SFR(Hα) = 2.1 ± 0.2 M⊙ yr−1 is obtained using
the high-redshift (z ≳ 4) calibrations in I. G. Kramarenko et al. (2026), which
might be more appropriate for a young dwarf galaxy with a bursty star formation
history. The star formation rates are low, but in line with a main-sequence galaxy
with (extrapolating the relation from J. S. Speagle et al. 2014). Assuming zero
dust attenuation, the UV absolute magnitude (MUV = −16.7 ± 0.7; Section 3.1) would
imply SFR(UV) = 0.18 ± 0.12 M⊙ yr−1 (R. C. Kennicutt & N. J. Evans 2012). The discrepancy
between the UV and Hα inferred star formation rate suggests there is some amount
of dust attenuation in the host galaxy.\r\n\r\nWe derive a dynamical mass from the
width of the narrow component Hα line and the estimated UV size as , adopting the
empirical virial correction K(n)K(q) from A. van der Wel et al. (2022), where K(n)
and K(q) are functions of the best-fit ellipticity and Sérsic index (see Appendix
B). Adopting a Mdyn/M* factor of 40 as found by A. de Graaff et al. (2024) for dwarf
galaxies at high redshift, we infer a stellar mass of . However, the Mdyn/M* is
very uncertain in this regime, and the uncertainty can span over 1 dex (A. Saldana-Lopez
et al. 2025). We advise caution in interpreting this result, as there are large
uncertainties in the measurements of the narrow Hα component, the HST morphology,
and the empirical relations used.\r\n\r\nAs discussed in Section 4, the absorption
profile is compatible with broadening by a rotating disk wind, and numerical modeling
of such configurations often predicts a narrow component arising from increased
transmission due to purely kinematic effects in the wind geometry (D. Proga et al.
2000; D. Proga 2003; D. Proga & T. R. Kallman 2004). This would be an alternative
explanation for at least part of the narrow component flux. On the other hand, most
LRDs present narrow [O iii] emission that is often associated with the host galaxy.
Indeed, the ionized gas producing [O iii] emission should have associated emission
in the Hα and higher-order Balmer lines. However, constraining this component largely
depends on the assumptions on dust attenuation or ISM conditions, and requires very
high S/N and resolution data. Deep, space-based follow-up observations of PAN-BH*-1
would be very constraining for the wind kinematics (e.g., by the joint analysis
of Hβ) and to assess whether a narrow component comes from a host galaxy (e.g.,
by comparing to a narrow Hβ component or [O iii] λλ4960, 5008).\r\n\r\n5.2. Black
Hole Mass From Photosphere Models\r\nThe general physical setup of LRDs is an open
debate, and their masses are a major unknown. Due to the multiple differences with
respect to the classical AGN population, the validity of standard virial calibrations
has been questioned (e.g., V. Rusakov et al. 2026; J. E. Greene et al. 2026; A.
Sneppen et al. 2026; A. Torralba et al. 2026, although see, e.g., M. Brazzini et
al. 2025, 2026; J. Scholtz et al. 2026 for an alternative interpretation).\r\n\r\nOne
can obtain a mass estimate assuming a system in radiative equilibrium with Lbol/LEdd
= 1 (e.g., H. Umeda et al. 2026); this yields a total mass of ≈106 M⊙, using the
bolometric luminosity from integrating the best-fit blackbody in Section 3.1. Recently,
H. Liu et al. (2026) developed a synthetic spectral library of LRD atmosphere models.
In these models, the density of the photosphere is regulated by the net surface
gravity of an optically thick atmosphere, enabling constraints on the mass of the
system. We fit the JWST photometry of PAN-BH*-1 using the models from H. Liu et
al. (2026), assuming a negligible contribution from a host galaxy to the optical
continuum. The best-fit model has effective temperature Teff = 4800 K, surface gravity
, and metallicity (; see Figure 1). The best-fit implies a total mass of the system
(BH plus gas) of (Equation (6) in H. Liu et al. 2026, assuming hydrostatic equilibrium).
For the second and third best fits, we obtain and −2, respectively (, respectively;
with the same metallicity and effective temperature), which would imply lower limits
to the system mass between and 4. The bolometric luminosity of PAN-BH*-1 (from the
integral of the best-fit green curve in Figure 1) implies an Eddington luminosity
ratio of L/LEdd ≲ 13, assuming the best-fit mass from the H. Liu et al. (2026) models.
The elevated Eddington ratio is in line with the hypothesis of a radiation-driven
wind discussed in Section 4, and allows for somewhat larger system masses. The low
masses obtained with this model, combined with the stellar mass inferred from dynamical
arguments for the host galaxy (Section 3.3) set lower limits to the BH-to-stellar
mass ratio of MBH/M* ≳ 10−4–10−2, which are compatible with the relations observed
in the Local Universe, within the large uncertainties (A. E. Reines & M. Volonteri
2015).\r\n\r\n6. Conclusions\r\nIn this Letter, we presented the discovery and spectroscopic
confirmation of PAN-BH*-1, an LRD with an extreme Balmer break at z = 1.731. The
strength of the Balmer break (F115W/F814W = 7 ± 1) is comparable to the most extreme
LRDs known, The Cliff (A. de Graaff et al. 2025a) and MoM-BH* (R. P. Naidu et al.
2025). We summarize the observations and our main conclusions as follows.\r\n\r\n\r\n1.
\ \r\nWe obtained deep VLT/X-Shooter spectroscopy of PAN-BH*-1. The Hα emission
line is luminous and broad (LHα = 1043 erg s−1), and has an unusually strong absorption.
Hβ is detected with an S/N ≈ 6, and we conservatively estimate a lower limit for
the Balmer decrement of Hα/Hβ > 9.4 (at a 3σ confidence level), in line with other
LRDs in the literature (e.g., A. de Graaff et al. 2025b; G. P. Nikopoulos et al.
2026).\r\n2. \r\nThe absorption trough spans from −520 to 267 km s−1 (at a transmission
level of 99%). We interpret the presence of blue- and redshifted absorption as produced
by a disk wind, analogous to those analyzed in the context of broad absorption line
quasars or accreting stars. This hypothesis would imply that the source of the optical
continuum is likely a thick photospheric disk.\r\n3. \r\nWe detect a narrow Hα
component (FWHM = 184 ± 12 km s−1), which we interpret as probing a host galaxy
with M* ≈ 108 M⊙ and SFR = 2–3 M⊙. This interpretation is in line with the extended
rest-NUV morphology measured in the HST bands (\r\n kpc).\r\n4. \r\nBy fitting
the synthetic atmosphere models of H. Liu et al. (2026), we estimate a system mass
(BH+envelope) of 104–106 M⊙. The inferred masses, together with the stellar mass
inferred from morphology and narrow emission line dynamics, imply BH-to-stellar
mass ratios of 10−2–10−4, close to the extrapolated trend in the local Universe
(A. E. Reines & M. Volonteri 2015).\r\n5. \r\nThe confirmation of this source at
cosmic noon (magnitude of ≈22 in the K band, Hα flux ≈5 × 10−16 erg s−1 cm−2) proves
the feasibility of detecting extreme LRDs at such epochs with wide-area spectroscopic
surveys like Euclid or the forthcoming Nancy Grace Roman Space Telescope.\r\n\r\nAcknowledgments\r\nA.T.
thanks Debasish Dutta and Tamara Bogdanović for useful conversations about stellar
and AGN winds.\r\n\r\nWe thank the scientific referee for the useful and constructive
feedback, which helped improve the quality of this paper.\r\n\r\nJ.M. and A.T. acknowledge
funding by the European Union (ERC, AGENTS, 101076224). The work of CCW is supported
by NOIRLab, which is managed by the Association of Universities for Research in
Astronomy (AURA) under a cooperative agreement with the National Science Foundation.
A.P.C. warmly acknowledges the support of the National Science Foundation through
the NSF Graduate Research Fellowship Program. A.d.G. acknowledges support from a
Clay Fellowship awarded by the Smithsonian Astrophysical Observatory.\r\n\r\nBased
on observations made with ESO Telescopes at the Paranal Observatory under program
IDs 116.294D and 116.2AQ0.\r\n\r\nThis work is based in part on observations made
with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the
Mikulski Archive for Space Telescopes at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in Astronomy,
Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated
with programs #2514 and #9433. C.C.W. gratefully acknowledges support for program
JWST-GO-2514 provided by NASA through a grant from the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in Astronomy,
Inc., under NASA contract NAS 5-03127. The authors acknowledge the team led by co-PIs
R. Maiolino and F. D’Eugenio for developing their observing program with a zero-exclusive-access
period.\r\n\r\nThis research is based on observations made with the NASA/ESA Hubble
Space Telescope obtained from the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc., under NASA contract
NAS 5–26555. These observations are associated with program #15117.\r\n\r\nThe JWST
and HST data presented in this article were obtained from the Mikulski Archive for
Space Telescopes (MAST) at the Space Telescope Science Institute. The specific observations
analyzed can be accessed via doi:10.17909/ydwx-st06.\r\n\r\nThis work is based in
part on observations made with the Spitzer Space Telescope, which was operated by
the Jet Propulsion Laboratory, California Institute of Technology under a contract
with NASA. The Spitzer data used in this work can be found in doi:10.26131/IRSA3.\r\n\r\nThis
work was supported by the International Space Science Institute (ISSI) in Bern,
through ISSI International Team project #25-659 “Little Red Dots, Big Open Questions.”\r\n\r\nJWST
cartoon in Figure 6, credit: NASA.\r\n\r\nFacilities: VLT:Kueyen - Very Large Telescope
(Kueyen) (X-Shooter), VLT:Yepun (HAWK-I), JWST - James Webb Space Telescope (NIRCam,
NIRspec), HST - Hubble Space Telescope satellite (ACS), Spitzer - Spitzer Space
Telescope satellite (IRAC, MIPS) - .\r\n\r\nSoftware: astropy (Astropy Collaboration
et al. 2013, 2018; Astropy Collaboration et al. 2022), NumPy (C. R. Harris et al.
2020), SciPy (P. Virtanen et al. 2020), pysersic (I. Pasha & T. B. Miller 2023),
stpsf (M. D. Perrin et al. 2014), lmfit (M. Newville et al. 2014), EsoRex (ESO CPL
Development Team 2015), Claude (used for Python coding; https://claude.ai/), SEP
(K. Barbary 2016)."
article_number: L37
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Alberto
full_name: Torralba Torregrosa, Alberto
id: 018f0249-0e87-11f0-b167-cbce08fbd541
last_name: Torralba Torregrosa
orcid: 0000-0001-5586-6950
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Andrea
full_name: Weibel, Andrea
last_name: Weibel
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: Yilun
full_name: Ma, Yilun
last_name: Ma
- first_name: Aidan P.
full_name: Cloonan, Aidan P.
last_name: Cloonan
- first_name: Aayush A
full_name: Desai, Aayush A
id: 502cfd30-32c1-11ee-a9a4-d8dad5c6739e
last_name: Desai
- first_name: Anna
full_name: De Graaff, Anna
last_name: De Graaff
- first_name: Jenny E.
full_name: Greene, Jenny E.
last_name: Greene
- first_name: Christian Kragh
full_name: Jespersen, Christian Kragh
last_name: Jespersen
- first_name: Ivan
full_name: Kramarenko, Ivan
id: 9a9394cb-3200-11ee-973b-f5ba2a8b16e4
last_name: Kramarenko
orcid: 0000-0001-5346-6048
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: Pascal A.
full_name: Oesch, Pascal A.
last_name: Oesch
- first_name: Wendy Q.
full_name: Sun, Wendy Q.
last_name: Sun
- first_name: Christina C.
full_name: Williams, Christina C.
last_name: Williams
citation:
ama: 'Torralba Torregrosa A, Matthee JJ, Weibel A, et al. A black hole star at cosmic
noon: Extreme Balmer break, photospheric continuum, and broad absorption by thick
winds in a Little Red Dot at z = 1.7. The Astrophysical Journal Letters.
2026;1005(2). doi:10.3847/2041-8213/ae7bfd'
apa: 'Torralba Torregrosa, A., Matthee, J. J., Weibel, A., Naidu, R. P., Ma, Y.,
Cloonan, A. P., … Williams, C. C. (2026). A black hole star at cosmic noon: Extreme
Balmer break, photospheric continuum, and broad absorption by thick winds in a
Little Red Dot at z = 1.7. The Astrophysical Journal Letters. IOP Publishing.
https://doi.org/10.3847/2041-8213/ae7bfd'
chicago: 'Torralba Torregrosa, Alberto, Jorryt J Matthee, Andrea Weibel, Rohan P.
Naidu, Yilun Ma, Aidan P. Cloonan, Aayush A Desai, et al. “A Black Hole Star at
Cosmic Noon: Extreme Balmer Break, Photospheric Continuum, and Broad Absorption
by Thick Winds in a Little Red Dot at z = 1.7.” The Astrophysical Journal Letters.
IOP Publishing, 2026. https://doi.org/10.3847/2041-8213/ae7bfd.'
ieee: 'A. Torralba Torregrosa et al., “A black hole star at cosmic noon:
Extreme Balmer break, photospheric continuum, and broad absorption by thick winds
in a Little Red Dot at z = 1.7,” The Astrophysical Journal Letters, vol.
1005, no. 2. IOP Publishing, 2026.'
ista: 'Torralba Torregrosa A, Matthee JJ, Weibel A, Naidu RP, Ma Y, Cloonan AP,
Desai AA, De Graaff A, Greene JE, Jespersen CK, Kramarenko I, Mascia S, Oesch
PA, Sun WQ, Williams CC. 2026. A black hole star at cosmic noon: Extreme Balmer
break, photospheric continuum, and broad absorption by thick winds in a Little
Red Dot at z = 1.7. The Astrophysical Journal Letters. 1005(2), L37.'
mla: 'Torralba Torregrosa, Alberto, et al. “A Black Hole Star at Cosmic Noon: Extreme
Balmer Break, Photospheric Continuum, and Broad Absorption by Thick Winds in a
Little Red Dot at z = 1.7.” The Astrophysical Journal Letters, vol. 1005,
no. 2, L37, IOP Publishing, 2026, doi:10.3847/2041-8213/ae7bfd.'
short: A. Torralba Torregrosa, J.J. Matthee, A. Weibel, R.P. Naidu, Y. Ma, A.P.
Cloonan, A.A. Desai, A. De Graaff, J.E. Greene, C.K. Jespersen, I. Kramarenko,
S. Mascia, P.A. Oesch, W.Q. Sun, C.C. Williams, The Astrophysical Journal Letters
1005 (2026).
corr_author: '1'
das_tickbox: '1'
dataavailabilitystatement: "Based on observations made with ESO Telescopes at the
Paranal Observatory under program IDs 116.294D and 116.2AQ0.\r\n\r\nThis work is
based in part on observations made with the NASA/ESA/CSA James Webb Space Telescope.
The data were obtained from the Mikulski Archive for Space Telescopes at the Space
Telescope Science Institute, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These
observations are associated with programs #2514 and #9433. C.C.W. gratefully acknowledges
support for program JWST-GO-2514 provided by NASA through a grant from the Space
Telescope Science Institute, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS 5-03127. The authors acknowledge
the team led by co-PIs R. Maiolino and F. D’Eugenio for developing their observing
program with a zero-exclusive-access period.\r\n\r\nThis research is based on observations
made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope
Science Institute, which is operated by the Association of Universities for Research
in Astronomy, Inc., under NASA contract NAS 5–26555. These observations are associated
with program #15117.\r\n\r\nThe JWST and HST data presented in this article were
obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope
Science Institute. The specific observations analyzed can be accessed via doi:10.17909/ydwx-st06.\r\n\r\nThis
work is based in part on observations made with the Spitzer Space Telescope, which
was operated by the Jet Propulsion Laboratory, California Institute of Technology
under a contract with NASA. The Spitzer data used in this work can be found in doi:10.26131/IRSA3.\r\n\r\nThis
work was supported by the International Space Science Institute (ISSI) in Bern,
through ISSI International Team project #25-659 “Little Red Dots, Big Open Questions.”\r\n\r\nJWST
cartoon in Figure 6, credit: NASA.\r\n\r\nFacilities: VLT:Kueyen - Very Large Telescope
(Kueyen) (X-Shooter), VLT:Yepun (HAWK-I), JWST - James Webb Space Telescope (NIRCam,
NIRspec), HST - Hubble Space Telescope satellite (ACS), Spitzer - Spitzer Space
Telescope satellite (IRAC, MIPS) - .\r\n\r\nSoftware: astropy (Astropy Collaboration
et al. 2013, 2018; Astropy Collaboration et al. 2022), NumPy (C. R. Harris et al.
2020), SciPy (P. Virtanen et al. 2020), pysersic (I. Pasha & T. B. Miller 2023),
stpsf (M. D. Perrin et al. 2014), lmfit (M. Newville et al. 2014), EsoRex (ESO CPL
Development Team 2015), Claude (used for Python coding; https://claude.ai/), SEP
(K. Barbary 2016)."
date_created: 2026-07-12T22:02:17Z
date_published: 2026-07-10T00:00:00Z
date_updated: 2026-07-13T08:08:41Z
day: '10'
ddc:
- '520'
department:
- _id: JoMa
- _id: IlCa
- _id: GradSch
doi: 10.3847/2041-8213/ae7bfd
external_id:
arxiv:
- '2603.28335'
file:
- access_level: open_access
checksum: 7600db260d799ddea45cf3bd01effe41
content_type: application/pdf
creator: dernst
date_created: 2026-07-13T07:46:22Z
date_updated: 2026-07-13T07:46:22Z
file_id: '22274'
file_name: 2026_AstrophysicalJourLetters_Torralba.pdf
file_size: 5419071
relation: main_file
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file_date_updated: 2026-07-13T07:46:22Z
has_accepted_license: '1'
intvolume: ' 1005'
issue: '2'
language:
- iso: eng
month: '07'
oa: 1
oa_version: Published Version
project:
- _id: bd9b2118-d553-11ed-ba76-db24564edfea
grant_number: '101076224'
name: Young galaxies as tracers and agents of cosmic reionization
publication: The Astrophysical Journal Letters
publication_identifier:
eissn:
- 2041-8213
issn:
- 2041-8205
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
researchdata_availability: yes
scopus_import: '1'
status: public
supplementarymaterial: yes
title: 'A black hole star at cosmic noon: Extreme Balmer break, photospheric continuum,
and broad absorption by thick winds in a Little Red Dot at z = 1.7'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 1005
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
PlanS_conform: '1'
_id: '22264'
abstract:
- lang: eng
text: 'The correlation between galaxy stellar mass and gas-phase metallicity, known
as the mass–metallicity relation (MZR), gives key insights into the processes
that govern galaxy evolution. However, unquantified observational and selection
biases can result in systematic errors in attempts to recover the intrinsic MZR,
particularly at higher redshifts. We characterize the MZR at z ∼ 3–6 within a
fully Bayesian framework using JWST/NIRSpec spectra of 191 galaxies from the RUBIES
survey. We forward model the observed mass–metallicity surface using prospector-generated
spectra to account for two selection biases: the survey selection function and
the success in observing high signal-to-noise ratio emission lines. We demonstrate
that the RUBIES selection function, based on F444W magnitude and F150W – F444W
color, has a negligible effect on our measured MZR. A correct treatment of the
non-Gaussian metallicity uncertainties from strong-line calibrations lowers the
derived MZR normalization by 0.2 dex and flattens the slope by ∼20%; forward modeling
the effect of emission line observability steepens the slope by ∼15%. Both of
these biases must be taken into account in order to properly measure the intrinsic
MZR. This novel forward-modeling process motivates careful consideration of selection
functions in future surveys, and paves the way for robust, high-redshift chemical
enrichment studies that trace the evolution of the MZR across cosmic time.'
acknowledgement: "This work is based on observations made with the NASA/ESA/CSA James
Webb Space Telescope. The data were obtained from the Mikulski Archive for Space
Telescopes at the Space Telescope Science Institute, which is operated by the Association
of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127
for JWST. These observations are associated with program ID 4233. This material
is based upon work supported by the National Science Foundation Graduate Research
Fellowship under grant No. 2137424 as well as work supported by NASA under Award
No. 2025_3-0, issued through the Wisconsin Space Grant Consortium, and JWST-GO-4233.
Any opinions, findings, and conclusions or recommendations expressed in this material
are those of the author(s) and do not necessarily reflect the views of the National
Aeronautics and Space Administration. Support for program ID 4233 was provided by
NASA through a grant from the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc., under NASA contract
NAS 5-03127. M.V.M. is supported by the National Science Foundation via grant AAG
2205519. A.d.G. acknowledges support from a Clay Fellowship awarded by the Smithsonian
Astrophysical Observatory. T.B.M. was supported by a CIERA Fellowship. Part of the
computations for this research were performed on the Pennsylvania State University’s
Institute for Computational and Data Sciences’ Roar supercomputer. Some/all of the
data presented in this article were obtained from the Mikulski Archive for Space
Telescopes (MAST) at the Space Telescope Science Institute. The specific observations
analyzed can be accessed via doi:10.17909/qk5z-7p30. The scripts used to generate
the data and results in this work can be found in Zenodo at doi:10.5281/zenodo.20513668
and GitHub \r\nhttps://github.com/zachlewis99/rubies_mzr "
article_number: '159'
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Zach
full_name: Lewis, Zach
last_name: Lewis
- first_name: Michael V.
full_name: Maseda, Michael V.
last_name: Maseda
- first_name: Anna
full_name: De Graaff, Anna
last_name: De Graaff
- first_name: Joel
full_name: Leja, Joel
last_name: Leja
- first_name: Bingjie
full_name: Wang, Bingjie
last_name: Wang
- first_name: Hans Walter
full_name: Rix, Hans Walter
last_name: Rix
- first_name: Ian
full_name: Mcconachie, Ian
last_name: Mcconachie
- first_name: Nikko J.
full_name: Cleri, Nikko J.
last_name: Cleri
- first_name: Rachel
full_name: Bezanson, Rachel
last_name: Bezanson
- first_name: Leindert A.
full_name: Boogaard, Leindert A.
last_name: Boogaard
- first_name: Gabriel
full_name: Brammer, Gabriel
last_name: Brammer
- first_name: Jenny E.
full_name: Greene, Jenny E.
last_name: Greene
- first_name: Michaela
full_name: Hirschmann, Michaela
last_name: Hirschmann
- first_name: Harley
full_name: Katz, Harley
last_name: Katz
- first_name: Ivo
full_name: Labbé, Ivo
last_name: Labbé
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Tim B.
full_name: Miller, Tim B.
last_name: Miller
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: Pascal A.
full_name: Oesch, Pascal A.
last_name: Oesch
- first_name: David J.
full_name: Setton, David J.
last_name: Setton
- first_name: Katherine A.
full_name: Suess, Katherine A.
last_name: Suess
- first_name: Andrea
full_name: Weibel, Andrea
last_name: Weibel
- first_name: Katherine E.
full_name: Whitaker, Katherine E.
last_name: Whitaker
- first_name: Christina C.
full_name: Williams, Christina C.
last_name: Williams
citation:
ama: Lewis Z, Maseda MV, De Graaff A, et al. The mass–metallicity relation and its
observational effects at z ∼ 3–6. The Astrophysical Journal. 2026;1005(2).
doi:10.3847/1538-4357/ae7bfc
apa: Lewis, Z., Maseda, M. V., De Graaff, A., Leja, J., Wang, B., Rix, H. W., …
Williams, C. C. (2026). The mass–metallicity relation and its observational effects
at z ∼ 3–6. The Astrophysical Journal. IOP Publishing. https://doi.org/10.3847/1538-4357/ae7bfc
chicago: Lewis, Zach, Michael V. Maseda, Anna De Graaff, Joel Leja, Bingjie Wang,
Hans Walter Rix, Ian Mcconachie, et al. “The Mass–Metallicity Relation and Its
Observational Effects at z ∼ 3–6.” The Astrophysical Journal. IOP Publishing,
2026. https://doi.org/10.3847/1538-4357/ae7bfc.
ieee: Z. Lewis et al., “The mass–metallicity relation and its observational
effects at z ∼ 3–6,” The Astrophysical Journal, vol. 1005, no. 2. IOP Publishing,
2026.
ista: Lewis Z, Maseda MV, De Graaff A, Leja J, Wang B, Rix HW, Mcconachie I, Cleri
NJ, Bezanson R, Boogaard LA, Brammer G, Greene JE, Hirschmann M, Katz H, Labbé
I, Matthee JJ, Miller TB, Naidu RP, Oesch PA, Setton DJ, Suess KA, Weibel A, Whitaker
KE, Williams CC. 2026. The mass–metallicity relation and its observational effects
at z ∼ 3–6. The Astrophysical Journal. 1005(2), 159.
mla: Lewis, Zach, et al. “The Mass–Metallicity Relation and Its Observational Effects
at z ∼ 3–6.” The Astrophysical Journal, vol. 1005, no. 2, 159, IOP Publishing,
2026, doi:10.3847/1538-4357/ae7bfc.
short: Z. Lewis, M.V. Maseda, A. De Graaff, J. Leja, B. Wang, H.W. Rix, I. Mcconachie,
N.J. Cleri, R. Bezanson, L.A. Boogaard, G. Brammer, J.E. Greene, M. Hirschmann,
H. Katz, I. Labbé, J.J. Matthee, T.B. Miller, R.P. Naidu, P.A. Oesch, D.J. Setton,
K.A. Suess, A. Weibel, K.E. Whitaker, C.C. Williams, The Astrophysical Journal
1005 (2026).
das_tickbox: '1'
dataavailabilitystatement: The specific observations analyzed can be accessed via
doi:10.17909/qk5z-7p30. The scripts used to generate the data and results in this
work can be found in Zenodo at doi:10.5281/zenodo.20513668 and GitHub https://github.com/zachlewis99/rubies_mzr
date_created: 2026-07-12T22:02:17Z
date_published: 2026-07-10T00:00:00Z
date_updated: 2026-07-13T07:40:41Z
day: '10'
ddc:
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department:
- _id: JoMa
doi: 10.3847/1538-4357/ae7bfc
external_id:
arxiv:
- '2512.03134'
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intvolume: ' 1005'
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keyword:
- Galaxy evolution
- Chemical enrichment
- Metallicity
- Galaxy abundances
- Scaling relations
language:
- iso: eng
month: '07'
oa: 1
oa_version: Published Version
publication: The Astrophysical Journal
publication_identifier:
eissn:
- 1538-4357
issn:
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supplementarymaterial: no
title: The mass–metallicity relation and its observational effects at z ∼ 3–6
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...