---
OA_place: publisher
OA_type: diamond
PlanS_conform: '1'
_id: '22369'
abstract:
- lang: eng
text: The high-redshift progenitors of present-day galaxy clusters are believed
to substantially contribute to the global star formation rate density and drive
the large-scale reionisation of the Universe. Here we present a blind and unbiased
search for and characterisation of galaxy overdensities during the reionisation
epoch at redshifts z ∼ 5.5 − 7 based on rest-frame optical JWST/NIRCam grism spectroscopy
of the Abell 2744 lensing field as part of the JWST All the Little Things (ALT)
survey. Using a physically motivated, cosmological inference friends-of-friends
(FoF) algorithm, we identified six galaxy overdensities, including five robust
systems at z = 5.66–6.77. They are all characterised by total halo masses of Mhalo ≳ 1011 M⊙,
inferred from a range of proxies. We find that the galaxy members in these overdense
environments are on average less massive though equally metal-rich, and generally
comprised of younger stellar populations, as indicated by their bluer spectral
slopes and less prominent Balmer breaks compared to field galaxies at similar
redshifts. Further, we use this novel rest-frame optical selection of galaxy proto-clusters
to infer the fraction and 3D distribution of strong Lyman-α emitters (LAEs) and
damped Lyman-α absorbers (DLAs) in the overdensity environments. We find that
two out of the six galaxy overdensities have excess H I absorption compared to
the field average, while the other four are consistent within their large scatter
in density. These results present the first direct observational constraints on
the tomography of the dense, neutral gas reservoirs in large-scale galaxy overdensities
at z > 5 and highlight the limitations of pre-JWST searches for reionisation-era
galaxy overdensities relying on the detection of strong LAEs alone.
acknowledgement: 'We would like to thank the anonymous referee for their positive
and constructive report and all the observers world-wide for their substantial effort
in securing all the public JWST data that were essential for this work. The Cosmic
Dawn Center (DAWN) is funded by the Danish National Research Foundation under grant
DNRF140. KEH acknowledges support from the Independent Research Fund Denmark (DFF)
under grant 5251-00009B and co-funding by the European Union (ERC, HEAVYMETAL, 101071865).
Views and opinions expressed are, however, those of the authors only and do not
necessarily reflect those of the European Union or the European Research Council.
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 (MAST) 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. We used the following software for this work: Python, and
the scientific Python ecosystem, in particular NumPy (Harris et al. 2020), SciPy
(including cKDTree) (Virtanen et al. 2021), Matplotlib (Hunter 2007), and Astropy
(Astropy Collaboration 2013, 2018, 2022).'
article_number: A290
article_processing_charge: No
article_type: original
author:
- first_name: Chamilla
full_name: Terp, Chamilla
last_name: Terp
- first_name: Kasper E.
full_name: Heintz, Kasper E.
last_name: Heintz
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: Pascal A.
full_name: Oesch, Pascal A.
last_name: Oesch
- first_name: Callum
full_name: Witten, Callum
last_name: Witten
- first_name: Daichi
full_name: Kashino, Daichi
last_name: Kashino
- first_name: Clara L.
full_name: Pollock, Clara L.
last_name: Pollock
- first_name: Claudia
full_name: Di Cesare, Claudia
id: 2d002343-372f-11ef-98ec-a164d20427cb
last_name: Di Cesare
- first_name: Alberto
full_name: Torralba Torregrosa, Alberto
id: 018f0249-0e87-11f0-b167-cbce08fbd541
last_name: Torralba Torregrosa
orcid: 0000-0001-5586-6950
citation:
ama: 'Terp C, Heintz KE, Matthee JJ, et al. All the massive galaxy overdensities
during reionisation: JWST rest-frame optical selection reveals young, chemically
evolved galaxies embedded in dense, neutral gas at z > 5. Astronomy &
Astrophysics. 2026;710. doi:10.1051/0004-6361/202659436'
apa: 'Terp, C., Heintz, K. E., Matthee, J. J., Naidu, R. P., Oesch, P. A., Witten,
C., … Torralba Torregrosa, A. (2026). All the massive galaxy overdensities during
reionisation: JWST rest-frame optical selection reveals young, chemically evolved
galaxies embedded in dense, neutral gas at z > 5. Astronomy & Astrophysics.
EDP Sciences. https://doi.org/10.1051/0004-6361/202659436'
chicago: 'Terp, Chamilla, Kasper E. Heintz, Jorryt J Matthee, Rohan P. Naidu, Pascal
A. Oesch, Callum Witten, Daichi Kashino, Clara L. Pollock, Claudia Di Cesare,
and Alberto Torralba Torregrosa. “All the Massive Galaxy Overdensities during
Reionisation: JWST Rest-Frame Optical Selection Reveals Young, Chemically Evolved
Galaxies Embedded in Dense, Neutral Gas at z > 5.” Astronomy & Astrophysics.
EDP Sciences, 2026. https://doi.org/10.1051/0004-6361/202659436.'
ieee: 'C. Terp et al., “All the massive galaxy overdensities during reionisation:
JWST rest-frame optical selection reveals young, chemically evolved galaxies embedded
in dense, neutral gas at z > 5,” Astronomy & Astrophysics, vol.
710. EDP Sciences, 2026.'
ista: 'Terp C, Heintz KE, Matthee JJ, Naidu RP, Oesch PA, Witten C, Kashino D, Pollock
CL, Di Cesare C, Torralba Torregrosa A. 2026. All the massive galaxy overdensities
during reionisation: JWST rest-frame optical selection reveals young, chemically
evolved galaxies embedded in dense, neutral gas at z > 5. Astronomy &
Astrophysics. 710, A290.'
mla: 'Terp, Chamilla, et al. “All the Massive Galaxy Overdensities during Reionisation:
JWST Rest-Frame Optical Selection Reveals Young, Chemically Evolved Galaxies Embedded
in Dense, Neutral Gas at z > 5.” Astronomy & Astrophysics, vol.
710, A290, EDP Sciences, 2026, doi:10.1051/0004-6361/202659436.'
short: C. Terp, K.E. Heintz, J.J. Matthee, R.P. Naidu, P.A. Oesch, C. Witten, D.
Kashino, C.L. Pollock, C. Di Cesare, A. Torralba Torregrosa, Astronomy & Astrophysics
710 (2026).
das_tickbox: '1'
dataavailabilitystatement: The specific observations analysed in this work can be
accessed via https://doi.org/10.5281/zenodo.13871850
date_created: 2026-07-19T22:01:47Z
date_published: 2026-06-01T00:00:00Z
date_updated: 2026-07-20T13:42:20Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1051/0004-6361/202659436
file:
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has_accepted_license: '1'
intvolume: ' 710'
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'
researchdata_availability: yes
scopus_import: '1'
status: public
supplementarymaterial: yes
title: 'All the massive galaxy overdensities during reionisation: JWST rest-frame
optical selection reveals young, chemically evolved galaxies embedded in dense,
neutral gas at z > 5'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
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...