---
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
relation: main_file
success: 1
file_date_updated: 2026-02-24T07:46:47Z
fulldoi: https://doi.org/10.1051/0004-6361/202556597
has_accepted_license: '1'
intvolume: ' 706'
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: 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
volume: 706
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
fulldoi: https://doi.org/10.1051/0004-6361/202557537
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
fulldoi: https://doi.org/10.1051/0004-6361/202557790
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'
...
---
OA_place: publisher
OA_type: gold
_id: '21710'
abstract:
- lang: eng
text: "Early results from JWST suggest that Epoch of Reionization (EoR) galaxies
produce copious ionizing photons, which, if they escape efficiently, could cause
reionization to occur too early. We study this problem using JWST imaging and
prism spectroscopy for 412 galaxies at 4.5 < z < 9.0. We fit these data simultaneously
with stellar population and nebular emission models that include a parameter for
the fraction of ionizing photons that escape the galaxy, fesc. We find that the
ionization production efficiency, ξion = Q(H0)/LUV, increases with redshift and
decreasing UV luminosity, but shows significant scatter, (log ion z, MUV) 0.3
dex. The inferred escape fractions averaged over the population are low, ranging
from〈fesc〉 ≃ 2.6% ± 1.4% at 6 < z < 9 to 6.5% ± 2.2% at 4.5 < z < 6, with weak
or no indication of evolution with redshift. This implies that in our models most
of the ionizing photons need to be absorbed to account for the nebular emission.
We compute the impact of our results on reionization, including the distributions
for ξion and fesc, and the evolution and uncertainty of the UV luminosity function.
Considering galaxies brighter than MUV < −16 mag would produce an intergalactic
medium hydrogen-ionized fraction of xe = 0.5 at 5.3 < z < 5.8, possibly too late
compared to constraints from from quasistellar\r\nobject (QSO) sight lines. Including
fainter galaxies, MUV < −14 mag, we obtain xe = 0.5 at 6.0 < z < 8.1, fully consistent
with QSO and cosmic microwave background data. This implies that EoR galaxies
produce plenty of ionizing photons, but that these do not efficiently escape.
This may be a result of high gas column densities combined with burstier star
formation histories, which limit the time massive stars are able to clear channels
through the gas for ionizing photons to escape."
acknowledgement: "We wish to thank our colleagues in the CEERS collaboration for their
hard work and valuable contributions on this project. We extend our sincerest thanks
to the anonymous referee whose critical and constructive report improved the quality
of this manuscript. We also thank the JADES team for providing an excellent dataset
for science. We with to thank colleagues for valuable discussions, feedback, and
suggestions, including John Chisholm, Kevin Huffenberger, Jessica\r\nMeh, Julian
Muñoz, Irene Shivaei, Justin Spilker, Aaron Smith, and Romain Teyssier.\r\nPortions
of this research were conducted with the advanced computing resources provided by
Texas A&M High Performance Research Computing (HPRC, http://hprc.tamu.edu). This
work benefited from support from the George P. and Cynthia Woods Mitchell Institute
for Fundamental Physics and Astronomy at Texas A&M University. CP thanks Marsha
and Ralph Schilling for generous support of this research. This work was partially
support by the Future Investigators in NASA Earth and Space Science and Technology
(FINESST) program grant No. 80NSSC23K1487. R.A. acknowledges support of grant PID2023-147386NB-I00
funded by MICIU/AEI/10.13039/501100011033 and by ERDF/EU, and the Severo Ochoa grant
CEX2021-001131-S funded by MCIN/AEI/10.13039/50110001103. A.C.C. acknowledges support
from a UKRI Frontier Research Guarantee Grant (PI Carnall; grant reference EP/Y037065/1)
This work acknowledges support from the NASA/ESA/CSA James Webb Space Telescope
through the\r\nSpace Telescope Science Institute, which is operated by the Association
of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-03127.
Support for program JWST-ERS-01345.009-A, JWST-GO-02079.013-A, JWST-GO-06368.011-A,
and JWST-GO-01837.030-A, 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. This work made use of v2.2
of the Binary Population\r\nand Spectral Synthesis (BPASS) models as described in
E. R. Stanway & J. J. Eldridge (2018)."
article_number: '111'
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Casey
full_name: Papovich, Casey
last_name: Papovich
- first_name: Justin W.
full_name: Cole, Justin W.
last_name: Cole
- first_name: Weida
full_name: Hu, Weida
last_name: Hu
- first_name: Steven L.
full_name: Finkelstein, Steven L.
last_name: Finkelstein
- first_name: Lu
full_name: Shen, Lu
last_name: Shen
- first_name: Pablo
full_name: Arrabal Haro, Pablo
last_name: Arrabal Haro
- first_name: Ricardo O.
full_name: Amorín, Ricardo O.
last_name: Amorín
- first_name: Bren E.
full_name: Backhaus, Bren E.
last_name: Backhaus
- first_name: Micaela B.
full_name: Bagley, Micaela B.
last_name: Bagley
- first_name: Rachana
full_name: Bhatawdekar, Rachana
last_name: Bhatawdekar
- first_name: Antonello
full_name: Calabrò, Antonello
last_name: Calabrò
- first_name: Adam C.
full_name: Carnall, Adam C.
last_name: Carnall
- first_name: Nikko J.
full_name: Cleri, Nikko J.
last_name: Cleri
- first_name: Emanuele
full_name: Daddi, Emanuele
last_name: Daddi
- first_name: Mark
full_name: Dickinson, Mark
last_name: Dickinson
- first_name: Norman A.
full_name: Grogin, Norman A.
last_name: Grogin
- first_name: Benne W.
full_name: Holwerda, Benne W.
last_name: Holwerda
- first_name: Anne E.
full_name: Jaskot, Anne E.
last_name: Jaskot
- first_name: Anton M.
full_name: Koekemoer, Anton M.
last_name: Koekemoer
- first_name: Mario
full_name: Llerena, Mario
last_name: Llerena
- first_name: Ray A.
full_name: Lucas, Ray A.
last_name: Lucas
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: Fabio
full_name: Pacucci, Fabio
last_name: Pacucci
- first_name: Laura
full_name: Pentericci, Laura
last_name: Pentericci
- first_name: Pablo G.
full_name: Pérez-González, Pablo G.
last_name: Pérez-González
- first_name: Nor
full_name: Pirzkal, Nor
last_name: Pirzkal
- first_name: Srinivasan
full_name: Raghunathan, Srinivasan
last_name: Raghunathan
- first_name: Lise Marie
full_name: Seillé, Lise Marie
last_name: Seillé
- first_name: Rachel S.
full_name: Somerville, Rachel S.
last_name: Somerville
- first_name: L. Y.Aaron
full_name: Yung, L. Y.Aaron
last_name: Yung
citation:
ama: Papovich C, Cole JW, Hu W, et al. Galaxies in the epoch of reionization are
all bark and no bite-plenty of ionizing photons, low escape fractions. The
Astrophysical Journal. 2026;1000(1). doi:10.3847/1538-4357/ae3b25
apa: Papovich, C., Cole, J. W., Hu, W., Finkelstein, S. L., Shen, L., Arrabal Haro,
P., … Yung, L. Y. A. (2026). Galaxies in the epoch of reionization are all bark
and no bite-plenty of ionizing photons, low escape fractions. The Astrophysical
Journal. IOP Publishing. https://doi.org/10.3847/1538-4357/ae3b25
chicago: Papovich, Casey, Justin W. Cole, Weida Hu, Steven L. Finkelstein, Lu Shen,
Pablo Arrabal Haro, Ricardo O. Amorín, et al. “Galaxies in the Epoch of Reionization
Are All Bark and No Bite-Plenty of Ionizing Photons, Low Escape Fractions.” The
Astrophysical Journal. IOP Publishing, 2026. https://doi.org/10.3847/1538-4357/ae3b25.
ieee: C. Papovich et al., “Galaxies in the epoch of reionization are all
bark and no bite-plenty of ionizing photons, low escape fractions,” The Astrophysical
Journal, vol. 1000, no. 1. IOP Publishing, 2026.
ista: Papovich C, Cole JW, Hu W, Finkelstein SL, Shen L, Arrabal Haro P, Amorín
RO, Backhaus BE, Bagley MB, Bhatawdekar R, Calabrò A, Carnall AC, Cleri NJ, Daddi
E, Dickinson M, Grogin NA, Holwerda BW, Jaskot AE, Koekemoer AM, Llerena M, Lucas
RA, Mascia S, Pacucci F, Pentericci L, Pérez-González PG, Pirzkal N, Raghunathan
S, Seillé LM, Somerville RS, Yung LYA. 2026. Galaxies in the epoch of reionization
are all bark and no bite-plenty of ionizing photons, low escape fractions. The
Astrophysical Journal. 1000(1), 111.
mla: Papovich, Casey, et al. “Galaxies in the Epoch of Reionization Are All Bark
and No Bite-Plenty of Ionizing Photons, Low Escape Fractions.” The Astrophysical
Journal, vol. 1000, no. 1, 111, IOP Publishing, 2026, doi:10.3847/1538-4357/ae3b25.
short: C. Papovich, J.W. Cole, W. Hu, S.L. Finkelstein, L. Shen, P. Arrabal Haro,
R.O. Amorín, B.E. Backhaus, M.B. Bagley, R. Bhatawdekar, A. Calabrò, A.C. Carnall,
N.J. Cleri, E. Daddi, M. Dickinson, N.A. Grogin, B.W. Holwerda, A.E. Jaskot, A.M.
Koekemoer, M. Llerena, R.A. Lucas, S. Mascia, F. Pacucci, L. Pentericci, P.G.
Pérez-González, N. Pirzkal, S. Raghunathan, L.M. Seillé, R.S. Somerville, L.Y.A.
Yung, The Astrophysical Journal 1000 (2026).
date_created: 2026-04-12T22:01:49Z
date_published: 2026-03-20T00:00:00Z
date_updated: 2026-05-04T10:44:57Z
day: '20'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.3847/1538-4357/ae3b25
external_id:
arxiv:
- '2505.08870'
file:
- access_level: open_access
checksum: 0031a6f197a3fa8c2845de10b6bdc696
content_type: application/pdf
creator: dernst
date_created: 2026-05-04T10:40:07Z
date_updated: 2026-05-04T10:40:07Z
file_id: '21791'
file_name: 2026_AstrophysicalJour_Papovich.pdf
file_size: 6670398
relation: main_file
success: 1
file_date_updated: 2026-05-04T10:40:07Z
fulldoi: https://doi.org/10.3847/1538-4357/ae3b25
has_accepted_license: '1'
intvolume: ' 1000'
issue: '1'
language:
- iso: eng
month: '03'
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: Galaxies in the epoch of reionization are all bark and no bite-plenty of ionizing
photons, low escape fractions
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
OA_type: diamond
PlanS_conform: '1'
_id: '21934'
abstract:
- lang: eng
text: "An accurate characterisation of the physical properties of galaxies at cosmic
dawn is key to understanding\r\nthe origin of the high abundance of UV-bright
galaxies at z≳10. We exploit deep (9.1-hour exposure time)\r\nNIRSpec PRISM observations
of GHZ2 to constrain the sources of ionising radiation and the properties of the\r\ninterstellar
medium (ISM) in this bright, compact, and highly ionising galaxy at z=12.3. We
measure with\r\nhigh significance the prominent N IV, C IV, He II, O III, C III,
O II, and Ne III emission features previously\r\ndetected in shallower observations,
and confirm the detection of the N III] λ1750 multiplet, yielding tight\r\nconstraints
on the N/O ratio, which is found to be ≃2 times the solar value. We also detect
the Mg II λ2800,\r\n[Fe IV] λ2833 and Si II λ1812 doublets, the H8+HeI λλ3889
blend, and the Si IV+O IV] λλ1400 absorption\r\ncomplex. The O III λ3133 fluorescence
line is only detected in the first observing epoch, implying variability\r\non
a rest-frame time span of 19 days, strongly suggesting the presence of an active
nucleus. Combining the\r\nNIRSpec dataset with available optical and far-infrared
constraints from MIRI and ALMA, we show that the\r\nemission spectrum of GHZ2
cannot be reproduced by single-density spectro-photometric models, even under\r\nextreme
assumptions on the ionisation parameter and electron density. Multi-zone photoionisation
modelling\r\nperformed with the HOMERUN code demonstrates that star formation
must be occurring in a strongly stratified\r\nISM, where both low-/intermediate-density
gas and high-density regions (log(ne/cm−3\r\n) ≳ 4) coexist. The\r\nGHZ2 emission
landscape is consistent with either a composite star-formation plus AGN scenario,
or with\r\nstar formation occurring in a combination of radiation- and matter-bounded
regions. Purely radiation-bounded\r\nstellar models fail to reproduce the observed
He II emission, making an additional hard ionising component\r\nunavoidable."
acknowledgement: "We thank the referee for the constructive comments that\r\nhelped
us improve the manuscript. We thank S. Finkelstein,\r\nY. Harikane, C. Mason, and
D. Stark for the useful comments.\r\nWe thank Tony Roman (Program Coordinator) and
Glenn\r\nWahlgren (NIRSpec reviewer) for the assistance in the\r\npreparation of
GO-3073 observations. This work is based\r\non observations made with the NASA/ESA/CSA
James\r\nWebb Space Telescope (JWST). The JWST data presented in this article were
obtained from the Mikulski Archive for\r\nSpace Telescopes (MAST) at the Space Telescope
Science\r\nInstitute. The specific observations analysed are associated with program
JWST-GO-3073 and can be accessed\r\nvia https://doi.org/10.17909/4r6b-bx96 (first
pointing) and\r\nhttps://doi:10.17909/zq4g-r525 (second pointing). We\r\nacknowledge
financial support from NASA through grant\r\nJWST-ERS-1324 and JWST-GO-3073. Support
was also\r\nprovided by the PRIN 2022 MUR project 2022CB3PJ3 –\r\nFirst Light And
Galaxy aSsembly (FLAGS) funded by the\r\nEuropean Union – Next Generation EU, by
INAF GO Grant\r\n2024 ”Revealing the nature of bright galaxies at cosmic\r\ndawn
with deep JWST spectroscopy”, by INAF Mini-grant\r\n2022 “Reionization and Fundamental
Cosmology with\r\nHigh-Redshift Galaxies”, and by INAF Large Grant 2022\r\n“Extragalactic
Surveys with JWST”. L.N. acknowledges\r\nsupport from grant “Progetti per Avvio
alla Ricerca - Tipo\r\n1, Unveiling Cosmic Dawn: Galaxy Evolution with CAPERS” (AR1241906F947685).
EV acknowledges financial\r\nsupport through grants INAF GO Grant 2024 “Mapping
Star\r\nCluster Feedback in a Galaxy 450 Myr after the Big Bang”\r\nand by the European
Union – NextGenerationEU within\r\nPRIN 2022 project n.20229YBSAN - Globular clusters\r\nin
cosmological simulations and lensed fields: from their\r\nbirth to the present epoch.
AM acknowledges support\r\nfrom project PRIN-MUR project “PROMETEUS” financed\r\nby
the European Union - Next Generation EU, Mission 4\r\nComponent 1 CUP B53D2300475000.
AM acknowledges\r\nsupport from Ricerca Fondamentale INAF under Mini Grant\r\n2023
”Quantitative Spectroscopy of Ionized Nebulae and\r\nGalaxies (QSING)” and under
Data Analysis Grant 2024\r\n“Accurate measurements of metallicity in galaxies with
a new\r\napproach to photoionization modelling”."
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: M.
full_name: Castellano, M.
last_name: Castellano
- first_name: L.
full_name: Napolitano, L.
last_name: Napolitano
- first_name: B.
full_name: Moreschini, B.
last_name: Moreschini
- first_name: A.
full_name: Calabrò, A.
last_name: Calabrò
- first_name: L.
full_name: Christensen, L.
last_name: Christensen
- first_name: M.
full_name: Llerena, M.
last_name: Llerena
- first_name: T. J.L.C.
full_name: Bakx, T. J.L.C.
last_name: Bakx
- first_name: F.
full_name: Belfiore, F.
last_name: Belfiore
- first_name: D.
full_name: Bevacqua, D.
last_name: Bevacqua
- first_name: M.
full_name: Dickinson, M.
last_name: Dickinson
- first_name: A.
full_name: Fontana, A.
last_name: Fontana
- first_name: G.
full_name: Gandolfi, G.
last_name: Gandolfi
- first_name: T.
full_name: Gasparetto, T.
last_name: Gasparetto
- first_name: A.
full_name: Marconi, A.
last_name: Marconi
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: E.
full_name: Merlin, E.
last_name: Merlin
- first_name: T.
full_name: Morishita, T.
last_name: Morishita
- first_name: T.
full_name: Nanayakkara, T.
last_name: Nanayakkara
- first_name: D.
full_name: Paris, D.
last_name: Paris
- first_name: L.
full_name: Pentericci, L.
last_name: Pentericci
- first_name: B.
full_name: Pérez-Díaz, B.
last_name: Pérez-Díaz
- first_name: G.
full_name: Roberts-Borsani, G.
last_name: Roberts-Borsani
- first_name: S.
full_name: Rojas-Ruiz, S.
last_name: Rojas-Ruiz
- first_name: P.
full_name: Santini, P.
last_name: Santini
- first_name: T.
full_name: Treu, T.
last_name: Treu
- first_name: E.
full_name: Vanzella, E.
last_name: Vanzella
- first_name: B.
full_name: Vulcani, B.
last_name: Vulcani
- first_name: X.
full_name: Wang, X.
last_name: Wang
- first_name: I.
full_name: Yoon, I.
last_name: Yoon
- first_name: J.
full_name: Zavala, J.
last_name: Zavala
citation:
ama: Castellano M, Napolitano L, Moreschini B, et al. Investigating ionising sources
and the complex interstellar medium of GHZ2 at z=12.3. The Open Journal of
Astrophysics. 2026;9. doi:10.33232/001c.160281
apa: Castellano, M., Napolitano, L., Moreschini, B., Calabrò, A., Christensen, L.,
Llerena, M., … Zavala, J. (2026). Investigating ionising sources and the complex
interstellar medium of GHZ2 at z=12.3. The Open Journal of Astrophysics.
Maynooth Academic Publishing. https://doi.org/10.33232/001c.160281
chicago: Castellano, M., L. Napolitano, B. Moreschini, A. Calabrò, L. Christensen,
M. Llerena, T. J.L.C. Bakx, et al. “Investigating Ionising Sources and the Complex
Interstellar Medium of GHZ2 at Z=12.3.” The Open Journal of Astrophysics.
Maynooth Academic Publishing, 2026. https://doi.org/10.33232/001c.160281.
ieee: M. Castellano et al., “Investigating ionising sources and the complex
interstellar medium of GHZ2 at z=12.3,” The Open Journal of Astrophysics,
vol. 9. Maynooth Academic Publishing, 2026.
ista: Castellano M, Napolitano L, Moreschini B, Calabrò A, Christensen L, Llerena
M, Bakx TJLC, Belfiore F, Bevacqua D, Dickinson M, Fontana A, Gandolfi G, Gasparetto
T, Marconi A, Mascia S, Merlin E, Morishita T, Nanayakkara T, Paris D, Pentericci
L, Pérez-Díaz B, Roberts-Borsani G, Rojas-Ruiz S, Santini P, Treu T, Vanzella
E, Vulcani B, Wang X, Yoon I, Zavala J. 2026. Investigating ionising sources and
the complex interstellar medium of GHZ2 at z=12.3. The Open Journal of Astrophysics.
9.
mla: Castellano, M., et al. “Investigating Ionising Sources and the Complex Interstellar
Medium of GHZ2 at Z=12.3.” The Open Journal of Astrophysics, vol. 9, Maynooth
Academic Publishing, 2026, doi:10.33232/001c.160281.
short: M. Castellano, L. Napolitano, B. Moreschini, A. Calabrò, L. Christensen,
M. Llerena, T.J.L.C. Bakx, F. Belfiore, D. Bevacqua, M. Dickinson, A. Fontana,
G. Gandolfi, T. Gasparetto, A. Marconi, S. Mascia, E. Merlin, T. Morishita, T.
Nanayakkara, D. Paris, L. Pentericci, B. Pérez-Díaz, G. Roberts-Borsani, S. Rojas-Ruiz,
P. Santini, T. Treu, E. Vanzella, B. Vulcani, X. Wang, I. Yoon, J. Zavala, The
Open Journal of Astrophysics 9 (2026).
date_created: 2026-05-31T22:02:14Z
date_published: 2026-04-09T00:00:00Z
date_updated: 2026-06-02T06:39:53Z
day: '09'
ddc:
- '520'
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- _id: JoMa
doi: 10.33232/001c.160281
external_id:
arxiv:
- '2512.08490'
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publication: The Open Journal of Astrophysics
publication_identifier:
eissn:
- 2565-6120
publication_status: published
publisher: Maynooth Academic Publishing
quality_controlled: '1'
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title: Investigating ionising sources and the complex interstellar medium of GHZ2
at z=12.3
tmp:
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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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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: 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: A weak Ly α halo for an extremely bright little red dot. Indications of enshrouded
supermassive black hole growth
tmp:
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legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
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short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 705
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abstract:
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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
success: 1
file_date_updated: 2026-07-13T07:46:22Z
fulldoi: https://doi.org/10.3847/2041-8213/ae7bfd
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: diamond
PlanS_conform: '1'
_id: '22817'
abstract:
- lang: eng
text: Using deep, medium-resolution, JWST rest-optical spectra of a sample of typical
star-forming galaxies (Lyman-break galaxies and Lyman-α emitters) from the LyC22
survey at z ∼ 3, we determined the nebular abundances of N, O, and Ne relative
to H for a subsample of 25 objects with a direct method based on auroral [O III]
λ4363 line detections. Our measurements increased the number of accurate N/O determinations
at z ∼ 2 − 4 using a homogeneous approach. We found a mean value of log(N/O) =
−+0.25−0.21 over a metallicity range of 12 + log(O/H) = 7.56 to 8.44. The observed
N/O ratio and scatter are indistinguishable from that observed in low-z galaxies
and H II regions over the same metallicity range, thus showing no redshift evolution
of N/O for typical galaxies over a significant fraction of cosmic time. We also
show that typical z ∼ 3 galaxies have a similar offset in the BPT diagram to galaxies
from the low-z Lyman Continuum Survey (LzLCS) when compared to the average of
SDSS galaxies, and we demonstrate that this offset is not due to enhanced nitrogen
abundances. Our results establish a basis for future studies of the evolution
of N and O at higher redshifts.
acknowledgement: "Y.I., N.G., R.M.-C., and D.S. acknowledge support from\r\nproject
No. 224866 carried out in the framework of the Joint Call “UkrainianSwiss Joint
Research Projects: Call for Proposals 2023”. This work is based in\r\npart on observations
made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from
the Mikulski Archive for Space Telescopes\r\nat the Space Telescope Science Institute,
which is operated by the Association\r\nof Universities for Research in Astronomy,
Inc., under NASA contract NAS 5-\r\n03127 for JWST. These observations are associated
with program # 1869. Support for program # 1869 was provided by NASA through a grant
from the Space\r\nTelescope Science Institute, which is operated by the Association
of Universities\r\nfor Research in Astronomy, Inc., under NASA contract NAS 5-03127"
article_number: A242
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: D.
full_name: Schaerer, D.
last_name: Schaerer
- first_name: Y. I.
full_name: Izotov, Y. I.
last_name: Izotov
- first_name: R.
full_name: Marques-Chaves, R.
last_name: Marques-Chaves
- first_name: C. C.
full_name: Steidel, C. C.
last_name: Steidel
- first_name: N.
full_name: Reddy, N.
last_name: Reddy
- first_name: A. E.
full_name: Shapley, A. E.
last_name: Shapley
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: J.
full_name: Chisholm, J.
last_name: Chisholm
- first_name: S. R.
full_name: Flury, S. R.
last_name: Flury
- first_name: N.
full_name: Guseva, N.
last_name: Guseva
- first_name: T.
full_name: Heckman, T.
last_name: Heckman
- first_name: A.
full_name: Henry, A.
last_name: Henry
- first_name: A. K.
full_name: Inoue, A. K.
last_name: Inoue
- first_name: I.
full_name: Jung, I.
last_name: Jung
- first_name: H.
full_name: Kusakabe, H.
last_name: Kusakabe
- first_name: K.
full_name: Mawatari, K.
last_name: Mawatari
- first_name: P.
full_name: Oesch, P.
last_name: Oesch
- first_name: G.
full_name: Östlin, G.
last_name: Östlin
- first_name: L.
full_name: Pentericci, L.
last_name: Pentericci
- first_name: N.
full_name: Roy, N.
last_name: Roy
- first_name: A.
full_name: Saldana-Lopez, A.
last_name: Saldana-Lopez
- first_name: R.
full_name: Sato, R.
last_name: Sato
- first_name: E.
full_name: Vanzella, E.
last_name: Vanzella
- first_name: A.
full_name: Verhamme, A.
last_name: Verhamme
- first_name: B.
full_name: Wang, B.
last_name: Wang
citation:
ama: Schaerer D, Izotov YI, Marques-Chaves R, et al. Nitrogen abundances in star-forming
galaxies 2.2 Gyr after the Big Bang are not elevated. Astronomy & Astrophysics.
2026;708. doi:10.1051/0004-6361/202556832
apa: Schaerer, D., Izotov, Y. I., Marques-Chaves, R., Steidel, C. C., Reddy, N.,
Shapley, A. E., … Wang, B. (2026). Nitrogen abundances in star-forming galaxies
2.2 Gyr after the Big Bang are not elevated. Astronomy & Astrophysics.
EDP Sciences. https://doi.org/10.1051/0004-6361/202556832
chicago: Schaerer, D., Y. I. Izotov, R. Marques-Chaves, C. C. Steidel, N. Reddy,
A. E. Shapley, Sara Mascia, et al. “Nitrogen Abundances in Star-Forming Galaxies
2.2 Gyr after the Big Bang Are Not Elevated.” Astronomy & Astrophysics.
EDP Sciences, 2026. https://doi.org/10.1051/0004-6361/202556832.
ieee: D. Schaerer et al., “Nitrogen abundances in star-forming galaxies 2.2
Gyr after the Big Bang are not elevated,” Astronomy & Astrophysics,
vol. 708. EDP Sciences, 2026.
ista: Schaerer D, Izotov YI, Marques-Chaves R, Steidel CC, Reddy N, Shapley AE,
Mascia S, Chisholm J, Flury SR, Guseva N, Heckman T, Henry A, Inoue AK, Jung I,
Kusakabe H, Mawatari K, Oesch P, Östlin G, Pentericci L, Roy N, Saldana-Lopez
A, Sato R, Vanzella E, Verhamme A, Wang B. 2026. Nitrogen abundances in star-forming
galaxies 2.2 Gyr after the Big Bang are not elevated. Astronomy & Astrophysics.
708, A242.
mla: Schaerer, D., et al. “Nitrogen Abundances in Star-Forming Galaxies 2.2 Gyr
after the Big Bang Are Not Elevated.” Astronomy & Astrophysics, vol.
708, A242, EDP Sciences, 2026, doi:10.1051/0004-6361/202556832.
short: D. Schaerer, Y.I. Izotov, R. Marques-Chaves, C.C. Steidel, N. Reddy, A.E.
Shapley, S. Mascia, J. Chisholm, S.R. Flury, N. Guseva, T. Heckman, A. Henry,
A.K. Inoue, I. Jung, H. Kusakabe, K. Mawatari, P. Oesch, G. Östlin, L. Pentericci,
N. Roy, A. Saldana-Lopez, R. Sato, E. Vanzella, A. Verhamme, B. Wang, Astronomy
& Astrophysics 708 (2026).
das_tickbox: '1'
dataavailabilitystatement: "The data used are publicly available at the Mikulski Archive
for Space Telescope (MAST),\r\nand can be accessed at https://dx.doi.org/10.17909/x6d5-vd44."
date_created: 2026-09-06T22:01:57Z
date_published: 2026-04-01T00:00:00Z
date_updated: 2026-09-09T12:59:51Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1051/0004-6361/202556832
external_id:
arxiv:
- '2601.06968'
file:
- access_level: open_access
checksum: 94cc1327f363d69995984b06e18e2645
content_type: application/pdf
creator: dernst
date_created: 2026-09-09T12:55:37Z
date_updated: 2026-09-09T12:55:37Z
file_id: '22890'
file_name: 2026_AstronomyAstrophysics_Schaerer.pdf
file_size: 591297
relation: main_file
success: 1
file_date_updated: 2026-09-09T12:55:37Z
fulldoi: https://doi.org/10.1051/0004-6361/202556832
has_accepted_license: '1'
intvolume: ' 708'
language:
- iso: eng
month: '04'
oa: 1
oa_version: Published Version
publication: Astronomy & Astrophysics
publication_identifier:
eissn:
- 1432-0746
issn:
- 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
researchdata_availability: yes
scopus_import: '1'
status: public
supplementarymaterial: no
title: Nitrogen abundances in star-forming galaxies 2.2 Gyr after the Big Bang are
not elevated
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: 708
year: '2026'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: diamond
PlanS_conform: '1'
_id: '20932'
abstract:
- lang: eng
text: Identifying Lyman continuum (LyC) leakers at intermediate redshifts is crucial
for understanding the properties of cosmic reionizers because the opacity of the
intergalactic medium (IGM) prevents the direct detection of LyC emission from
sources during the Epoch of Reionization (EoR). In this study, we confirm two
new LyC candidate leakers at z ∼ 3 in the Abell 2744 cluster field, with absolute
escape fractions (fesc) of 0.83−0.80+0.15 and 0.74−0.70+0.23, respectively. The
LyC emission was detected using HST/WFC3/F275W and F336W imaging. These two candidate
leakers appear to be faint (MUV = −17.61 ± 0.06 and −18.22 ± 0.10), exhibit blue
UV continuum slopes (β = −2.43 ± 0.05 and −1.92 ± 0.09), have low masses (M★ ∼ 107.51 ± 0.03
and 107.17 ± 0.15 M⊙) and Lyα equivalent widths of 90 ± 3 Å and 28 ± 12 Å, respectively.
These two LyC candidate leakers were detected in a catalog of 91 spectroscopically
confirmed sources using public spectra from the JWST and/or MUSE. We also analyzed
properties that were proposed as indirect indicators of LyC emission, such as
Lyα, the O32 ratio, and M★. We created a galaxy subsample that was selected according
to these properties, stacked the LyC observations of this subsample, and assessed
the limits of the escape fractions in the stacks. We aim to enhance our understanding
of LyC escape mechanisms and improve our predictions of the LyC fesc during the
EoR by analyzing the individual candidates and the stacks in the context of the
currently limited sample of known LyC leakers at z ∼ 3.
acknowledgement: 'We acknowledge support from the National Science Foundation of China
– 12225301, INAF Large grant “Spectroscopic survey with JWST” jand from PRIN 2022
MUR project 2022CB3PJ3 – First Light And Galaxy aSsembly (FLAGS) funded by the European
Union – Next Generation EU, and Postgraduate Scholarship Program under the grant
of China Scholarship Council. P.W. and B.V. acknowledge support from the INAF Mini
Grant ‘1.05.24.07.01 RSN1: Spatially Resolved Near-IR Emission of Intermediate-Redshift
Jellyfish Galaxies’ (PI Watson). We acknowledge A. Acebron, C. Grillo, and P. Rosati
for their fundamental contribution to the strong lensing analysis and results. We
also extend our gratitude to the JWST and HST teams for their efforts in designing,
building, and operating these transformative missions.'
article_number: A328
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Y.
full_name: Liu, Y.
last_name: Liu
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: L.
full_name: Pentericci, L.
last_name: Pentericci
- first_name: P.
full_name: Watson, P.
last_name: Watson
- first_name: A.
full_name: Alavi, A.
last_name: Alavi
- first_name: P.
full_name: Bergamini, P.
last_name: Bergamini
- first_name: M.
full_name: Bradač, M.
last_name: Bradač
- first_name: A.
full_name: Calabrò, A.
last_name: Calabrò
- first_name: K.
full_name: Glazebrook, K.
last_name: Glazebrook
- first_name: A.
full_name: Henry, A.
last_name: Henry
- first_name: M.
full_name: Llerena, M.
last_name: Llerena
- first_name: E.
full_name: Merlin, E.
last_name: Merlin
- first_name: B.
full_name: Metha, B.
last_name: Metha
- first_name: T.
full_name: Nanayakkara, T.
last_name: Nanayakkara
- first_name: L.
full_name: Napolitano, L.
last_name: Napolitano
- first_name: N.
full_name: Roy, N.
last_name: Roy
- first_name: B.
full_name: Siana, B.
last_name: Siana
- first_name: E.
full_name: Vanzella, E.
last_name: Vanzella
- first_name: B.
full_name: Vulcani, B.
last_name: Vulcani
- first_name: X.
full_name: Wang, X.
last_name: Wang
citation:
ama: Liu Y, Mascia S, Pentericci L, et al. A Lyman continuum analysis of ∼100 galaxies
at z spec∼ 3 in the Abell 2744 cluster field. Astronomy & Astrophysics.
2025;704. doi:10.1051/0004-6361/202556410
apa: Liu, Y., Mascia, S., Pentericci, L., Watson, P., Alavi, A., Bergamini, P.,
… Wang, X. (2025). A Lyman continuum analysis of ∼100 galaxies at z spec∼ 3 in
the Abell 2744 cluster field. Astronomy & Astrophysics. EDP Sciences.
https://doi.org/10.1051/0004-6361/202556410
chicago: Liu, Y., Sara Mascia, L. Pentericci, P. Watson, A. Alavi, P. Bergamini,
M. Bradač, et al. “A Lyman Continuum Analysis of ∼100 Galaxies at z Spec∼ 3 in
the Abell 2744 Cluster Field.” Astronomy & Astrophysics. EDP Sciences,
2025. https://doi.org/10.1051/0004-6361/202556410.
ieee: Y. Liu et al., “A Lyman continuum analysis of ∼100 galaxies at z spec∼
3 in the Abell 2744 cluster field,” Astronomy & Astrophysics, vol.
704. EDP Sciences, 2025.
ista: Liu Y, Mascia S, Pentericci L, Watson P, Alavi A, Bergamini P, Bradač M, Calabrò
A, Glazebrook K, Henry A, Llerena M, Merlin E, Metha B, Nanayakkara T, Napolitano
L, Roy N, Siana B, Vanzella E, Vulcani B, Wang X. 2025. A Lyman continuum analysis
of ∼100 galaxies at z spec∼ 3 in the Abell 2744 cluster field. Astronomy &
Astrophysics. 704, A328.
mla: Liu, Y., et al. “A Lyman Continuum Analysis of ∼100 Galaxies at z Spec∼ 3 in
the Abell 2744 Cluster Field.” Astronomy & Astrophysics, vol. 704,
A328, EDP Sciences, 2025, doi:10.1051/0004-6361/202556410.
short: Y. Liu, S. Mascia, L. Pentericci, P. Watson, A. Alavi, P. Bergamini, M. Bradač,
A. Calabrò, K. Glazebrook, A. Henry, M. Llerena, E. Merlin, B. Metha, T. Nanayakkara,
L. Napolitano, N. Roy, B. Siana, E. Vanzella, B. Vulcani, X. Wang, Astronomy &
Astrophysics 704 (2025).
date_created: 2026-01-04T23:01:35Z
date_published: 2025-12-01T00:00:00Z
date_updated: 2026-02-16T12:14:52Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1051/0004-6361/202556410
external_id:
arxiv:
- '2507.11045'
file:
- access_level: open_access
checksum: 3e6061f3c4bfb521b3333ea4913c241a
content_type: application/pdf
creator: dernst
date_created: 2026-01-05T09:26:17Z
date_updated: 2026-01-05T09:26:17Z
file_id: '20938'
file_name: 2025_AstronomyAstrophysics_Liu.pdf
file_size: 4642530
relation: main_file
success: 1
file_date_updated: 2026-01-05T09:26:17Z
fulldoi: https://doi.org/10.1051/0004-6361/202556410
has_accepted_license: '1'
intvolume: ' 704'
language:
- iso: eng
month: '12'
oa: 1
oa_version: Published Version
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: A Lyman continuum analysis of ∼100 galaxies at z spec∼ 3 in the Abell 2744
cluster 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: 704
year: '2025'
...
---
DOAJ_listed: '1'
OA_place: publisher
OA_type: diamond
PlanS_conform: '1'
_id: '21060'
abstract:
- lang: eng
text: "Compact, star-forming galaxies with high star formation rate surface densities
(ΣSFR) are often efficient Lyman continuum (LyC) emitters at z ≤ 4.5, likely because
intense stellar feedback creates low-density channels that allow photons to escape.
Irregular or disturbed morphologies, such as those resulting from mergers, can
also facilitate LyC escape by creating anisotropic gas distributions. We investigated
the influence of galaxy morphology on LyC production and escape at redshifts 5
≤ z ≤ 7 using observations from various James Webb Space Telescope (JWST) surveys.
Our sample consists of 436 sources, which are predominantly low-mass (∼10^8.15
M\f), star-forming galaxies with ionizing photon efficiency (ξion) values consistent
with canonical expectations. Since direct measurements of fesc are not possible
during the Epoch of Reionization (EoR), we predicted fesc for high-redshift galaxies
by applying survival analysis to a subsample of LyC emitters from the Low-Redshift
Lyman Continuum Survey (LzLCS), selected to be direct analogs of reionization-era
galaxies. We find that these galaxies exhibit, on average, modest predicted escape
fractions (∼0.04). In addition, we evaluated the correlation between morphological
features and LyC emission. Our findings indicate that neither ξion nor the predicted
fesc values show a significant correlation with the presence of merger signatures.
This suggests that in low-mass galaxies at z ≥ 5, strong morphological disturbances
are not the primary mechanism driving LyC emission and leakage. Instead, compactness
and star formation activity likely play a more pivotal role in regulating LyC
escape. "
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 programs GTO 1243, ERS 1345, DDT
2750, and GTO 1180, 1181, 3215, 1210, 1286. 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 support from the INAF Large Grant 2022 “Extragalactic Surveys
with JWST” (PI Pentericci). We acknowledge support from INAF Mini-grant “Reionization
and Fundamental Cosmology with High-Redshift Galaxies” and from PRIN 2022 MUR project
2022CB3PJ3 - First Light And Galaxy aSsembly (FLAGS) funded by the European Union
– Next Generation EU. RA acknowledges support of Grant PID2023-147386NB-I00 funded
by MICIU/AEI/10.13039/501100011033 and by ERDF/EU, and the Severo Ochoa grant CEX2021-001131-S
funded by MCIN/AEI/10.13039/50110001103. The project that gave rise to these results
received the support of a fellowship from the “la Caixa” Foundation (ID 100010434).
The fellowship code is LCF/BQ/PR24/12050015. LC acknowledges support from grants
PID2022-139567NB-I00 and PIB2021-127718NB-I00 funded by the Spanish Ministry of
Science and Innovation/State Agency of Research MCIN/AEI/10.13039/501100011033 and
by “ERDF A way of making Europe”.
article_number: A122
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: L.
full_name: Pentericci, L.
last_name: Pentericci
- first_name: M.
full_name: Llerena, M.
last_name: Llerena
- first_name: A.
full_name: Calabrò, A.
last_name: Calabrò
- 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: S.
full_name: Flury, S.
last_name: Flury
- first_name: F.
full_name: Pacucci, F.
last_name: Pacucci
- first_name: A.
full_name: Jaskot, A.
last_name: Jaskot
- first_name: R. O.
full_name: Amorín, R. O.
last_name: Amorín
- first_name: R.
full_name: Bhatawdekar, R.
last_name: Bhatawdekar
- first_name: M.
full_name: Castellano, M.
last_name: Castellano
- first_name: N.
full_name: Cleri, N.
last_name: Cleri
- first_name: L.
full_name: Costantin, L.
last_name: Costantin
- first_name: K.
full_name: Davis, K.
last_name: Davis
- first_name: Claudia
full_name: Di Cesare, Claudia
id: 2d002343-372f-11ef-98ec-a164d20427cb
last_name: Di Cesare
- first_name: M.
full_name: Dickinson, M.
last_name: Dickinson
- first_name: A.
full_name: Fontana, A.
last_name: Fontana
- first_name: Y.
full_name: Guo, Y.
last_name: Guo
- first_name: M.
full_name: Giavalisco, M.
last_name: Giavalisco
- first_name: B. W.
full_name: Holwerda, B. W.
last_name: Holwerda
- first_name: W.
full_name: Hu, W.
last_name: Hu
- first_name: M.
full_name: Huertas-Company, M.
last_name: Huertas-Company
- first_name: Intae
full_name: Jung, Intae
last_name: Jung
- first_name: J.
full_name: Kartaltepe, J.
last_name: Kartaltepe
- first_name: D.
full_name: Kashino, D.
last_name: Kashino
- first_name: A. M.
full_name: Koekemoer, A. M.
last_name: Koekemoer
- first_name: R. A.
full_name: Lucas, R. A.
last_name: Lucas
- first_name: J.
full_name: Lotz, J.
last_name: Lotz
- first_name: L.
full_name: Napolitano, L.
last_name: Napolitano
- first_name: S.
full_name: Jogee, S.
last_name: Jogee
- first_name: S.
full_name: Wilkins, S.
last_name: Wilkins
citation:
ama: Mascia S, Pentericci L, Llerena M, et al. Little impact of mergers and galaxy
morphology on the production and escape of ionizing photons in the early Universe.
Astronomy & Astrophysics. 2025;701. doi:10.1051/0004-6361/202553760
apa: Mascia, S., Pentericci, L., Llerena, M., Calabrò, A., Matthee, J. J., Flury,
S., … Wilkins, S. (2025). Little impact of mergers and galaxy morphology on the
production and escape of ionizing photons in the early Universe. Astronomy
& Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/202553760
chicago: Mascia, Sara, L. Pentericci, M. Llerena, A. Calabrò, Jorryt J Matthee,
S. Flury, F. Pacucci, et al. “Little Impact of Mergers and Galaxy Morphology on
the Production and Escape of Ionizing Photons in the Early Universe.” Astronomy
& Astrophysics. EDP Sciences, 2025. https://doi.org/10.1051/0004-6361/202553760.
ieee: S. Mascia et al., “Little impact of mergers and galaxy morphology on
the production and escape of ionizing photons in the early Universe,” Astronomy
& Astrophysics, vol. 701. EDP Sciences, 2025.
ista: Mascia S, Pentericci L, Llerena M, Calabrò A, Matthee JJ, Flury S, Pacucci
F, Jaskot A, Amorín RO, Bhatawdekar R, Castellano M, Cleri N, Costantin L, Davis
K, Di Cesare C, Dickinson M, Fontana A, Guo Y, Giavalisco M, Holwerda BW, Hu W,
Huertas-Company M, Jung I, Kartaltepe J, Kashino D, Koekemoer AM, Lucas RA, Lotz
J, Napolitano L, Jogee S, Wilkins S. 2025. Little impact of mergers and galaxy
morphology on the production and escape of ionizing photons in the early Universe.
Astronomy & Astrophysics. 701, A122.
mla: Mascia, Sara, et al. “Little Impact of Mergers and Galaxy Morphology on the
Production and Escape of Ionizing Photons in the Early Universe.” Astronomy
& Astrophysics, vol. 701, A122, EDP Sciences, 2025, doi:10.1051/0004-6361/202553760.
short: S. Mascia, L. Pentericci, M. Llerena, A. Calabrò, J.J. Matthee, S. Flury,
F. Pacucci, A. Jaskot, R.O. Amorín, R. Bhatawdekar, M. Castellano, N. Cleri, L.
Costantin, K. Davis, C. Di Cesare, M. Dickinson, A. Fontana, Y. Guo, M. Giavalisco,
B.W. Holwerda, W. Hu, M. Huertas-Company, I. Jung, J. Kartaltepe, D. Kashino,
A.M. Koekemoer, R.A. Lucas, J. Lotz, L. Napolitano, S. Jogee, S. Wilkins, Astronomy
& Astrophysics 701 (2025).
corr_author: '1'
date_created: 2026-01-28T15:24:24Z
date_published: 2025-09-01T00:00:00Z
date_updated: 2026-02-09T07:33:46Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1051/0004-6361/202553760
external_id:
arxiv:
- '2501.08268'
file:
- access_level: open_access
checksum: 990e384ca19e14b35296712d3b9e2919
content_type: application/pdf
creator: dernst
date_created: 2026-02-09T07:28:08Z
date_updated: 2026-02-09T07:28:08Z
file_id: '21166'
file_name: 2025_AstronomyAstrophysics_Mascia.pdf
file_size: 9994234
relation: main_file
success: 1
file_date_updated: 2026-02-09T07:28:08Z
fulldoi: https://doi.org/10.1051/0004-6361/202553760
has_accepted_license: '1'
intvolume: ' 701'
language:
- iso: eng
month: '09'
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: Little impact of mergers and galaxy morphology on the production and escape
of ionizing photons in the early Universe
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: 701
year: '2025'
...
---
OA_place: publisher
OA_type: diamond
_id: '19930'
abstract:
- lang: eng
text: We present an analysis of the UV continuum slope, β, using a sample of 726
galaxies with z > 4, selected from a mixture of JWST ERS, GTO, and GO observational
programs. We considered only spectroscopic data obtained with the low-resolution
(R ∼ 30 − 300) PRISM/CLEAR NIRSpec configuration. Studying the correlation between
β and MUV, we find an overall decreasing trend, described by β = ( − 0.055 ± 0.017)MUV + ( − 2.98 ± 0.34).
This is consistent with previous studies, where brighter galaxies show redder
β values. However, when analyzing the trend in separate redshift bins, we find
that at high redshift the relation becomes much flatter and is consistent with
a flat slope within 1σ. Furthermore, we find that β tends to decrease with redshift,
following β = ( − 0.075 ± 0.010)z + ( − 1.496 ± 0.056). This is consistent with
most recent results showing a steepening of the spectra at higher z. We selected
a sample of galaxies with extremely blue slopes (i.e., β < −2.6). Such slopes
are steeper than predicted by stellar evolution models – even for dust-free, young,
metal-poor populations – when the contribution of nebular emission is included.
We selected 44 extremely blue galaxies (XBGs) and investigated the possible physical
origin of their steep slopes by comparing them to a subsample of redder galaxies
(matched in Δz = ±0.5 and ΔMUV = ±0.2). We find that XBGs have younger stellar
populations, stronger ionization fields, lower dust attenuation, and lower but
not pristine metallicity (∼10% Z⊙) compared to red galaxies. However, these properties
alone cannot explain the extreme β values. Using indirect inference of Lyman continuum
escape with the most recent models, we estimated the escape fraction fesc > 10%
in at least 25% of the XBGs, whereas all the red sources exhibit much lower fesc
values. A reduced nebular continuum contribution – resulting from either a high
escape fraction or a bursty star formation history – is likely the origin of the
extremely blue slopes.
acknowledgement: We acknowledges support from the INAF Large Grant for Extragalactic
Surveys with JWST and from the PRIN 2022 MUR project 2022CB3PJ3 – First Light And
Galaxy aSsembly (FLAGS) funded by the European Union – Next Generation EU. PS acknowledges
INAF Mini Grant 2022 “The evolution of passive galaxies through cosmic time”. Part
of the research activities described in this paper were carried out with the contribution
of the Next Generation EU funds within the National Recovery and Resilience Plan
(PNRR), Mission 4 – Education and Research, Component 2 – From Research to Business
(M4C2), Investment Line 3.1 – Strengthening and creation of Research Infrastructures,
Project IR0000034 – “STILES – Strengthening the Italian Leadership in ELT and SKA”.
RA acknowledges support of Grant project PID2023-147386NB-I00 funded by MICIU/AEI/10.13039/501100011033
and by ERDF/EU, and the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/10.13039/50110001103.
article_number: A234
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: D.
full_name: Dottorini, D.
last_name: Dottorini
- first_name: A.
full_name: Calabrò, A.
last_name: Calabrò
- first_name: L.
full_name: Pentericci, L.
last_name: Pentericci
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: M.
full_name: Llerena, M.
last_name: Llerena
- first_name: L.
full_name: Napolitano, L.
last_name: Napolitano
- first_name: P.
full_name: Santini, P.
last_name: Santini
- first_name: G.
full_name: Roberts-Borsani, G.
last_name: Roberts-Borsani
- first_name: M.
full_name: Castellano, M.
last_name: Castellano
- first_name: R.
full_name: Amorin, R.
last_name: Amorin
- first_name: M.
full_name: Dickinson, M.
last_name: Dickinson
- first_name: A.
full_name: Fontana, A.
last_name: Fontana
- first_name: N.
full_name: Hathi, N.
last_name: Hathi
- first_name: M.
full_name: Hirschmann, M.
last_name: Hirschmann
- first_name: A. M.
full_name: Koekemoer, A. M.
last_name: Koekemoer
- first_name: R. A.
full_name: Lucas, R. A.
last_name: Lucas
- first_name: E.
full_name: Merlin, E.
last_name: Merlin
- first_name: A.
full_name: Morales, A.
last_name: Morales
- first_name: F.
full_name: Pacucci, F.
last_name: Pacucci
- first_name: S.
full_name: Wilkins, S.
last_name: Wilkins
- first_name: P.
full_name: Arrabal Haro, P.
last_name: Arrabal Haro
- first_name: M.
full_name: Bagley, M.
last_name: Bagley
- first_name: S. L.
full_name: Finkelstein, S. L.
last_name: Finkelstein
- first_name: J.
full_name: Kartaltepe, J.
last_name: Kartaltepe
- first_name: C.
full_name: Papovich, C.
last_name: Papovich
- first_name: N.
full_name: Pirzkal, N.
last_name: Pirzkal
citation:
ama: 'Dottorini D, Calabrò A, Pentericci L, et al. Evolution of the UV slope of
galaxies at cosmic morning (z > 4): The properties of extremely blue galaxies.
Astronomy & Astrophysics. 2025;698. doi:10.1051/0004-6361/202453267'
apa: 'Dottorini, D., Calabrò, A., Pentericci, L., Mascia, S., Llerena, M., Napolitano,
L., … Pirzkal, N. (2025). Evolution of the UV slope of galaxies at cosmic morning
(z > 4): The properties of extremely blue galaxies. Astronomy & Astrophysics.
EDP Sciences. https://doi.org/10.1051/0004-6361/202453267'
chicago: 'Dottorini, D., A. Calabrò, L. Pentericci, Sara Mascia, M. Llerena, L.
Napolitano, P. Santini, et al. “Evolution of the UV Slope of Galaxies at Cosmic
Morning (z > 4): The Properties of Extremely Blue Galaxies.” Astronomy
& Astrophysics. EDP Sciences, 2025. https://doi.org/10.1051/0004-6361/202453267.'
ieee: 'D. Dottorini et al., “Evolution of the UV slope of galaxies at cosmic
morning (z > 4): The properties of extremely blue galaxies,” Astronomy
& Astrophysics, vol. 698. EDP Sciences, 2025.'
ista: 'Dottorini D, Calabrò A, Pentericci L, Mascia S, Llerena M, Napolitano L,
Santini P, Roberts-Borsani G, Castellano M, Amorin R, Dickinson M, Fontana A,
Hathi N, Hirschmann M, Koekemoer AM, Lucas RA, Merlin E, Morales A, Pacucci F,
Wilkins S, Arrabal Haro P, Bagley M, Finkelstein SL, Kartaltepe J, Papovich C,
Pirzkal N. 2025. Evolution of the UV slope of galaxies at cosmic morning (z >
4): The properties of extremely blue galaxies. Astronomy & Astrophysics. 698,
A234.'
mla: 'Dottorini, D., et al. “Evolution of the UV Slope of Galaxies at Cosmic Morning
(z > 4): The Properties of Extremely Blue Galaxies.” Astronomy & Astrophysics,
vol. 698, A234, EDP Sciences, 2025, doi:10.1051/0004-6361/202453267.'
short: D. Dottorini, A. Calabrò, L. Pentericci, S. Mascia, M. Llerena, L. Napolitano,
P. Santini, G. Roberts-Borsani, M. Castellano, R. Amorin, M. Dickinson, A. Fontana,
N. Hathi, M. Hirschmann, A.M. Koekemoer, R.A. Lucas, E. Merlin, A. Morales, F.
Pacucci, S. Wilkins, P. Arrabal Haro, M. Bagley, S.L. Finkelstein, J. Kartaltepe,
C. Papovich, N. Pirzkal, Astronomy & Astrophysics 698 (2025).
date_created: 2025-06-29T22:01:15Z
date_published: 2025-06-01T00:00:00Z
date_updated: 2026-02-16T12:11:39Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1051/0004-6361/202453267
external_id:
arxiv:
- '2412.01623'
isi:
- '001510826300019'
file:
- access_level: open_access
checksum: 100f897d468de9d0113277c870035b62
content_type: application/pdf
creator: dernst
date_created: 2025-06-30T08:22:08Z
date_updated: 2025-06-30T08:22:08Z
file_id: '19932'
file_name: 2025_AstronomyAstrophysics_Dottorini.pdf
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fulldoi: https://doi.org/10.1051/0004-6361/202453267
has_accepted_license: '1'
intvolume: ' 698'
isi: 1
language:
- iso: eng
month: '06'
oa: 1
oa_version: Published Version
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: 'Evolution of the UV slope of galaxies at cosmic morning (z > 4): The properties
of extremely blue galaxies'
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: 698
year: '2025'
...
---
OA_place: publisher
OA_type: diamond
_id: '19967'
abstract:
- lang: eng
text: "Context. Investigating the ionizing emission of star-forming galaxies and
the escape fraction of ionizing photons is critical to understanding their contribution
to reionization and their impact on the surrounding environment. The number of
ionizing photons available to reionize the intergalactic medium (IGM) depends
on not only the abundance of galaxies but also their efficiency in producing ionizing
photons (ξion). This quantity is thus fundamental to quantify the role of faint
versus bright sources in driving this process, as we must assess their relative
contribution to the total ionizing emissivity.\r\n\r\nAims. Our goal is to estimate
the ξion using Balmer lines (Hα or Hβ) in a sample of 761 galaxies at 4 ≤ z ≤ 10
selected from different JWST spectroscopic surveys. We aim to determine the redshift
evolution of ξion and the relation of ξion with the physical properties of the
galaxies.\r\n\r\nMethods. We used the available HST and JWST photometry to perform
a spectral energy distribution (SED) fitting in the sample to determine their
physical properties and relate them with ξion. We used the BAGPIPES code for the
SED fitting and assumed a delayed exponential model for the star formation history.
We used the NIRSpec spectra from prism or grating configurations to estimate Balmer
luminosities, and then constrained ξion values after dust correction.\r\n\r\nResults.
We find a mean value of 1025.22 Hz erg−1 for ξion in the sample with an observed
scatter of 0.42 dex. We find an increase in the median values of ξion with redshift
from 1025.09 Hz erg−1 at z ∼ 4.18 to 1025.28 Hz erg−1 at z ∼ 7.14, confirming
the redshift evolution of ξion found in other studies. Regarding the relation
between ξion and physical properties, we find a decrease in ξion with increasing
stellar mass, indicating that low-mass galaxies are efficient producers of ionizing
photons. We also find an increase in ξion with increasing specific star formation
rate (sSFR) and increasing UV absolute magnitude. This indicates that faint galaxies
and galaxies with high sSFR are also efficient producers. We also investigated
the relation of ξion with the rest-frame equivalent width (EW) of [OIII]λ5007
and find that galaxies with the higher EW([OIII]λ5007) are more efficient producers
of ionizing photons, with the best fit leading to the relation log(ξion) = 0.43 × log(EW[OIII])+23.99.
Similarly, we find that galaxies with higher O32 = [OIII]λ5007/[OII]λλ3727,3729
and lower gas-phase metallicities (based on the R23 = ([OIII]λλ4959,5007+[OII]λλ3727,3729)/Hβ
calibration) show higher ξion values."
acknowledgement: We thank the anonymous referee for the detailed review and useful
suggestions that helped to improve this paper. We wish to thank all our colleagues
in the CEERS collaboration for their hard work and valuable contributions to this
project. We thank Pietro Bergamini for providing us with the magnification factors
for the lensed sources. MLl acknowledges support from the INAF Large Grant 2022
“Extragalactic Surveys with JWST” (PI L. Pentericci), the PRIN 2022 MUR project
2022CB3PJ3 – First Light And Galaxy aSsembly (FLAGS) funded by the European Union
– Next Generation EU, and INAF Mini-grant “Galaxies in the epoch of Reionization
and their analogs at lower redshift” (PI M. Llerena). RA acknowledges support of
grant PID2023-147386NB-I00 funded by MICIU/AEI/10.13039/501100011033 and by ERDF/EU,
and the Severo Ochoa grant CEX2021-001131-S This work is based on observations made
with the NASA/ESA/CSA James Webb Space Telescope (JWST). The JWST 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 are
associated with program JWST-GO-3073 and can be accessed via DOI. We acknowledge
support from INAF Mini-grant “Reionization and Fundamental Cosmology with High-Redshift
Galaxies”. This work has made extensive use of Python packages astropy (Astropy
Collaboration 2018), numpy (Harris et al. 2020), Matplotlib (Hunter 2007) and LiMe
(Fernández et al. 2024).
article_number: A302
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: M.
full_name: Llerena, M.
last_name: Llerena
- first_name: L.
full_name: Pentericci, L.
last_name: Pentericci
- first_name: L.
full_name: Napolitano, L.
last_name: Napolitano
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: R.
full_name: Amorín, R.
last_name: Amorín
- first_name: A.
full_name: Calabrò, A.
last_name: Calabrò
- first_name: M.
full_name: Castellano, M.
last_name: Castellano
- first_name: N. J.
full_name: Cleri, N. J.
last_name: Cleri
- first_name: M.
full_name: Giavalisco, M.
last_name: Giavalisco
- first_name: N. A.
full_name: Grogin, N. A.
last_name: Grogin
- first_name: N. P.
full_name: Hathi, N. P.
last_name: Hathi
- first_name: M.
full_name: Hirschmann, M.
last_name: Hirschmann
- first_name: A. M.
full_name: Koekemoer, A. M.
last_name: Koekemoer
- first_name: T.
full_name: Nanayakkara, T.
last_name: Nanayakkara
- first_name: F.
full_name: Pacucci, F.
last_name: Pacucci
- first_name: L.
full_name: Shen, L.
last_name: Shen
- first_name: S. M.
full_name: Wilkins, S. M.
last_name: Wilkins
- first_name: I.
full_name: Yoon, I.
last_name: Yoon
- first_name: L. Y.A.
full_name: Yung, L. Y.A.
last_name: Yung
- first_name: R.
full_name: Bhatawdekar, R.
last_name: Bhatawdekar
- first_name: R. A.
full_name: Lucas, R. A.
last_name: Lucas
- first_name: X.
full_name: Wang, X.
last_name: Wang
- first_name: P.
full_name: Arrabal Haro, P.
last_name: Arrabal Haro
- first_name: M. B.
full_name: Bagley, M. B.
last_name: Bagley
- first_name: S. L.
full_name: Finkelstein, S. L.
last_name: Finkelstein
- first_name: J. S.
full_name: Kartaltepe, J. S.
last_name: Kartaltepe
- first_name: E.
full_name: Merlin, E.
last_name: Merlin
- first_name: C.
full_name: Papovich, C.
last_name: Papovich
- first_name: N.
full_name: Pirzkal, N.
last_name: Pirzkal
- first_name: P.
full_name: Santini, P.
last_name: Santini
citation:
ama: Llerena M, Pentericci L, Napolitano L, et al. The ionizing photon production
efficiency of star-forming galaxies at z ∼ 4–10. Astronomy & Astrophysics.
2025;698. doi:10.1051/0004-6361/202453251
apa: Llerena, M., Pentericci, L., Napolitano, L., Mascia, S., Amorín, R., Calabrò,
A., … Santini, P. (2025). The ionizing photon production efficiency of star-forming
galaxies at z ∼ 4–10. Astronomy & Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/202453251
chicago: Llerena, M., L. Pentericci, L. Napolitano, Sara Mascia, R. Amorín, A. Calabrò,
M. Castellano, et al. “The Ionizing Photon Production Efficiency of Star-Forming
Galaxies at z ∼ 4–10.” Astronomy & Astrophysics. EDP Sciences, 2025.
https://doi.org/10.1051/0004-6361/202453251.
ieee: M. Llerena et al., “The ionizing photon production efficiency of star-forming
galaxies at z ∼ 4–10,” Astronomy & Astrophysics, vol. 698. EDP Sciences,
2025.
ista: Llerena M, Pentericci L, Napolitano L, Mascia S, Amorín R, Calabrò A, Castellano
M, Cleri NJ, Giavalisco M, Grogin NA, Hathi NP, Hirschmann M, Koekemoer AM, Nanayakkara
T, Pacucci F, Shen L, Wilkins SM, Yoon I, Yung LYA, Bhatawdekar R, Lucas RA, Wang
X, Arrabal Haro P, Bagley MB, Finkelstein SL, Kartaltepe JS, Merlin E, Papovich
C, Pirzkal N, Santini P. 2025. The ionizing photon production efficiency of star-forming
galaxies at z ∼ 4–10. Astronomy & Astrophysics. 698, A302.
mla: Llerena, M., et al. “The Ionizing Photon Production Efficiency of Star-Forming
Galaxies at z ∼ 4–10.” Astronomy & Astrophysics, vol. 698, A302, EDP
Sciences, 2025, doi:10.1051/0004-6361/202453251.
short: M. Llerena, L. Pentericci, L. Napolitano, S. Mascia, R. Amorín, A. Calabrò,
M. Castellano, N.J. Cleri, M. Giavalisco, N.A. Grogin, N.P. Hathi, M. Hirschmann,
A.M. Koekemoer, T. Nanayakkara, F. Pacucci, L. Shen, S.M. Wilkins, I. Yoon, L.Y.A.
Yung, R. Bhatawdekar, R.A. Lucas, X. Wang, P. Arrabal Haro, M.B. Bagley, S.L.
Finkelstein, J.S. Kartaltepe, E. Merlin, C. Papovich, N. Pirzkal, P. Santini,
Astronomy & Astrophysics 698 (2025).
date_created: 2025-07-06T22:01:23Z
date_published: 2025-06-20T00:00:00Z
date_updated: 2026-02-16T12:12:15Z
day: '20'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1051/0004-6361/202453251
external_id:
arxiv:
- '2412.01358'
isi:
- '001512479700026'
file:
- access_level: open_access
checksum: 92745034d9448d38b6b0394407ae39a0
content_type: application/pdf
creator: dernst
date_created: 2025-07-08T06:17:02Z
date_updated: 2025-07-08T06:17:02Z
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file_name: 2025_AstronomyAstrophysics_Llerena.pdf
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file_date_updated: 2025-07-08T06:17:02Z
fulldoi: https://doi.org/10.1051/0004-6361/202453251
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intvolume: ' 698'
isi: 1
language:
- iso: eng
month: '06'
oa: 1
oa_version: Published Version
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 ionizing photon production efficiency of star-forming galaxies at z ∼ 4–10
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: 698
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---
DOAJ_listed: '1'
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OA_type: gold
PlanS_conform: '1'
_id: '20661'
abstract:
- lang: eng
text: "We analyse James Webb Space Telescope (JWST) Near Infrared Imager and Slitless
Spectrograph (NIRISS) and Near Infrared Spectrograph (NIRSpec) spectroscopic observations
in the Abell 2744 galaxy cluster field. From approximately 120 candidates, we
identify 12 objects with at least two prominent emission lines among [O II] λ3727,
H β λ4861, [O III] λ4959, [O III] λ5007, and H α λ6563 that are spectroscopically
confirmed by both instruments. Our key findings reveal systematic differences
between the two spectrographs based on source morphology and shutter aperture
placement. Compact objects show comparable or higher\r\nintegrated flux in NIRSpec
relative to NIRISS (within 1σ uncertainties), while extended sources consistently
display higher flux in NIRISS measurements. This pattern reflects NIRSpec’s optimal
coverage for compact objects while potentially undersampling extended sources.
Quantitative analysis demonstrates that NIRSpec recovers at least 63 per cent
of NIRISS-measured flux when the slit covers >15 per cent of the source or when
Re < 1 kpc. For lower coverage or larger effective radii, the recovered flux varies
from 24 per cent to 63 per cent. When studying the H α λ6563/[O III] λ5007 emission
line ratio, we observe that\r\nmeasurements from these different spectrographs
can vary by up to ∼0.3 dex, with significant implications for metallicity and
star formation rate characterizations for individual galaxies. These results highlight
the importance of considering instrumental effects when combining multi-instrument
spectroscopic data and demonstrate that source morphology critically influences
flux\r\nrecovery between slit-based and slitless spectroscopic modes in JWST observations."
acknowledgement: "This research was supported in part by the Australian Research Council
Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through
project number CE170100013. This research was supported in part by The Dr Albert
Shimmins Fund through the Albert Shimmins Postgraduate Writing Up Award (University
of Melbourne). 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 programmes JWST-ERS-1324, JWST-GO-2561,
and JWST-DDT-2756. BV and PW acknowledge support from the INAF Large Grant 2022
‘Extragalactic Surveys with JWST’ (PI Pentericci), the INAF Mini\r\nGrant ‘1.05.24.07.01
RSN1: Spatially-Resolved Near-IR Emission of Intermediate-Redshift Jellyfish Galaxies’
(PI Watson), and are supported by the European Union – NextGenerationEU RFF M4C2
1.1 PRIN 2022 project 2022ZSL4BL INSIGHT. MB acknowledges support from the ERC Advanced
Grant FIRSTLIGHT and Slovenian national research agency ARIS through grants N1-0238
and P1-0188. "
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Nicolò
full_name: Dalmasso, Nicolò
last_name: Dalmasso
- first_name: Peter J.
full_name: Watson, Peter J.
last_name: Watson
- first_name: Tommaso
full_name: Treu, Tommaso
last_name: Treu
- first_name: Michele
full_name: Trenti, Michele
last_name: Trenti
- first_name: Benedetta
full_name: Vulcani, Benedetta
last_name: Vulcani
- first_name: Themiya
full_name: Nanayakkara, Themiya
last_name: Nanayakkara
- first_name: Maruša
full_name: Bradač, Maruša
last_name: Bradač
- first_name: Tucker
full_name: Jones, Tucker
last_name: Jones
- first_name: Kristan
full_name: Boyett, Kristan
last_name: Boyett
- first_name: Xin
full_name: Wang, Xin
last_name: Wang
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: Laura
full_name: Pentericci, Laura
last_name: Pentericci
citation:
ama: 'Dalmasso N, Watson PJ, Treu T, et al. Quantifying spectroscopic flux variations
between JWST NIRISS and NIRSpec: Slit losses in emission line measurements of
z ∼ 1-3 galaxies. Monthly Notices of the Royal Astronomical Society. 2025;544(2):1915-1925.
doi:10.1093/mnras/staf1837'
apa: 'Dalmasso, N., Watson, P. J., Treu, T., Trenti, M., Vulcani, B., Nanayakkara,
T., … Pentericci, L. (2025). Quantifying spectroscopic flux variations between
JWST NIRISS and NIRSpec: Slit losses in emission line measurements of z ∼ 1-3
galaxies. Monthly Notices of the Royal Astronomical Society. Oxford University
Press. https://doi.org/10.1093/mnras/staf1837'
chicago: 'Dalmasso, Nicolò, Peter J. Watson, Tommaso Treu, Michele Trenti, Benedetta
Vulcani, Themiya Nanayakkara, Maruša Bradač, et al. “Quantifying Spectroscopic
Flux Variations between JWST NIRISS and NIRSpec: Slit Losses in Emission Line
Measurements of z ∼ 1-3 Galaxies.” Monthly Notices of the Royal Astronomical
Society. Oxford University Press, 2025. https://doi.org/10.1093/mnras/staf1837.'
ieee: 'N. Dalmasso et al., “Quantifying spectroscopic flux variations between
JWST NIRISS and NIRSpec: Slit losses in emission line measurements of z ∼ 1-3
galaxies,” Monthly Notices of the Royal Astronomical Society, vol. 544,
no. 2. Oxford University Press, pp. 1915–1925, 2025.'
ista: 'Dalmasso N, Watson PJ, Treu T, Trenti M, Vulcani B, Nanayakkara T, Bradač
M, Jones T, Boyett K, Wang X, Mascia S, Pentericci L. 2025. Quantifying spectroscopic
flux variations between JWST NIRISS and NIRSpec: Slit losses in emission line
measurements of z ∼ 1-3 galaxies. Monthly Notices of the Royal Astronomical Society.
544(2), 1915–1925.'
mla: 'Dalmasso, Nicolò, et al. “Quantifying Spectroscopic Flux Variations between
JWST NIRISS and NIRSpec: Slit Losses in Emission Line Measurements of z ∼ 1-3
Galaxies.” Monthly Notices of the Royal Astronomical Society, vol. 544,
no. 2, Oxford University Press, 2025, pp. 1915–25, doi:10.1093/mnras/staf1837.'
short: N. Dalmasso, P.J. Watson, T. Treu, M. Trenti, B. Vulcani, T. Nanayakkara,
M. Bradač, T. Jones, K. Boyett, X. Wang, S. Mascia, L. Pentericci, Monthly Notices
of the Royal Astronomical Society 544 (2025) 1915–1925.
date_created: 2025-11-23T23:01:38Z
date_published: 2025-12-01T00:00:00Z
date_updated: 2025-12-01T15:23:21Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1093/mnras/staf1837
external_id:
arxiv:
- '2510.27036'
isi:
- '001615620500001'
file:
- access_level: open_access
checksum: 2caff0a3b81fed114408377323298b43
content_type: application/pdf
creator: dernst
date_created: 2025-11-24T09:02:04Z
date_updated: 2025-11-24T09:02:04Z
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month: '12'
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oa_version: Published Version
page: 1915-1925
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: 'Quantifying spectroscopic flux variations between JWST NIRISS and NIRSpec:
Slit losses in emission line measurements of z ∼ 1-3 galaxies'
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: 544
year: '2025'
...