---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
PlanS_conform: '1'
_id: '22815'
abstract:
- lang: eng
  text: The mass assembly and chemical enrichment of the first galaxies provide key
    insights into their star formation histories and the earliest stellar populations
    at cosmic dawn. Here we compile and utilise new, high-quality spectroscopic JWST/NIRSpec
    Prism observations from the JWST archive. In particular, we extend the wavelength
    coverage beyond the standard pipeline cut-off (5.3 μm) up to 5.5 μm, which enables
    for the first time a detailed examination of the rest-frame optical emission-line
    properties for galaxies at z ≈ 10. Crucially, the improved calibration allows
    us to detect Hβ and the [O III] λλ4959, 5007 doublet and resolve the auroral [O III]
    λ4363 line for the 11 galaxies in our sample (z = 9.3 − 10.0) to obtain direct
    Te-based metallicity measurements. We find that the interstellar medium (ISM)
    of all galaxies shows high ionisation fields and electron temperatures, with derived
    metallicities in the range 12 + log(O/H) = 7.1 − 8.3 (3–50% solar), consistent
    with previous strong-line diagnostics based on JWST data at high redshifts. We
    derive an empirical relation for MUV and 12 + log(O/H) at z ≈ 10, useful for future
    higher-redshift studies, and show that the sample galaxies are ‘typical’ star-forming
    galaxies though with relatively high specific star formation rates (median sSFR
    = SFRHβ/M★ = 38 Gyr−1) and with evidence of bursty star formation on 10 Myr versus
    100 Myr timescales (log10(SFR10/SFR100)≈0.7). Combining the rest-frame optical
    line analysis and detailed UV to optical spectro-photometric modelling, we determine
    the mass-metallicity relation (MZR) and the fundamental metallicity relation (FMR)
    of the sample, pushing the previous redshift frontier of these measurements to
    z = 10. These results, together with literature measurements, point to a gradually
    decreasing MZR at higher redshifts, with a break in the FMR at z ≈ 3, decreasing
    to metallicities ≈3× lower at z = 10 than observed in galaxies during the majority
    of cosmic time at z = 0 − 3, likely caused by massive pristine gas inflows diluting
    the observed metal abundances during early galaxy assembly at cosmic dawn.
acknowledgement: We would like to thank the referee for providing a comprehensive
  and constructive report, greatly improving the results presented in this work. We
  further express our greatest gratitude to the investigators on the major JWST observing
  programs, such as RUBIES, CAPERS, UNCOVER, and JADES. The work presented here would
  not have been possible without their major efforts in designing and obtaining the
  observational data included in our work here. The Cosmic Dawn Center (DAWN) is funded
  by the Danish National Research Foundation under grant DNRF140. The data products
  presented herein were retrieved from the DAWN JWST Archive (DJA). DJA is an initiative
  of the Cosmic Dawn Center, which is funded by the Danish National Research Foundation
  under grant DNRF140. 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. 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. Software used in this work includes MATPLOTLIB (Hunter 2007),
  NUMPY (Harris et al. 2020), SCIPY (Virtanen et al. 2020), and ASTROPY (Astropy Collaboration
  2013).
article_number: A203
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Clara L.
  full_name: Pollock, Clara L.
  last_name: Pollock
- first_name: Rashmi
  full_name: Gottumukkala, Rashmi
  last_name: Gottumukkala
- first_name: Kasper E.
  full_name: Heintz, Kasper E.
  last_name: Heintz
- first_name: Gabriel B.
  full_name: Brammer, Gabriel B.
  last_name: Brammer
- first_name: Guido
  full_name: Roberts-Borsani, Guido
  last_name: Roberts-Borsani
- first_name: Pascal A.
  full_name: Oesch, Pascal A.
  last_name: Oesch
- first_name: Joris
  full_name: Witstok, Joris
  last_name: Witstok
- first_name: Karla Z.
  full_name: Arellano-Córdova, Karla Z.
  last_name: Arellano-Córdova
- first_name: Fergus
  full_name: Cullen, Fergus
  last_name: Cullen
- first_name: Dirk
  full_name: Scholte, Dirk
  last_name: Scholte
- first_name: Chamilla
  full_name: Terp, Chamilla
  last_name: Terp
- first_name: Lucie
  full_name: Rowland, Lucie
  last_name: Rowland
- first_name: Albert
  full_name: Sneppen, Albert
  last_name: Sneppen
- first_name: Kei
  full_name: Ito, Kei
  last_name: Ito
- first_name: Francesco
  full_name: Valentino, Francesco
  last_name: Valentino
- 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: Darach
  full_name: Watson, Darach
  last_name: Watson
- first_name: Sune
  full_name: Toft, Sune
  last_name: Toft
citation:
  ama: Pollock CL, Gottumukkala R, Heintz KE, et al. Novel z ∼ 10 auroral line measurements
    extend the gradual offset of the fundamental metallicity relation deep into the
    first gigayear of cosmic time. <i>Astronomy &#38; Astrophysics</i>. 2026;708.
    doi:<a href="https://doi.org/10.1051/0004-6361/202556032">10.1051/0004-6361/202556032</a>
  apa: Pollock, C. L., Gottumukkala, R., Heintz, K. E., Brammer, G. B., Roberts-Borsani,
    G., Oesch, P. A., … Toft, S. (2026). Novel z ∼ 10 auroral line measurements extend
    the gradual offset of the fundamental metallicity relation deep into the first
    gigayear of cosmic time. <i>Astronomy &#38; Astrophysics</i>. EDP Sciences. <a
    href="https://doi.org/10.1051/0004-6361/202556032">https://doi.org/10.1051/0004-6361/202556032</a>
  chicago: Pollock, Clara L., Rashmi Gottumukkala, Kasper E. Heintz, Gabriel B. Brammer,
    Guido Roberts-Borsani, Pascal A. Oesch, Joris Witstok, et al. “Novel z ∼ 10 Auroral
    Line Measurements Extend the Gradual Offset of the Fundamental Metallicity Relation
    Deep into the First Gigayear of Cosmic Time.” <i>Astronomy &#38; Astrophysics</i>.
    EDP Sciences, 2026. <a href="https://doi.org/10.1051/0004-6361/202556032">https://doi.org/10.1051/0004-6361/202556032</a>.
  ieee: C. L. Pollock <i>et al.</i>, “Novel z ∼ 10 auroral line measurements extend
    the gradual offset of the fundamental metallicity relation deep into the first
    gigayear of cosmic time,” <i>Astronomy &#38; Astrophysics</i>, vol. 708. EDP Sciences,
    2026.
  ista: Pollock CL, Gottumukkala R, Heintz KE, Brammer GB, Roberts-Borsani G, Oesch
    PA, Witstok J, Arellano-Córdova KZ, Cullen F, Scholte D, Terp C, Rowland L, Sneppen
    A, Ito K, Valentino F, Matthee JJ, Watson D, Toft S. 2026. Novel z ∼ 10 auroral
    line measurements extend the gradual offset of the fundamental metallicity relation
    deep into the first gigayear of cosmic time. Astronomy &#38; Astrophysics. 708,
    A203.
  mla: Pollock, Clara L., et al. “Novel z ∼ 10 Auroral Line Measurements Extend the
    Gradual Offset of the Fundamental Metallicity Relation Deep into the First Gigayear
    of Cosmic Time.” <i>Astronomy &#38; Astrophysics</i>, vol. 708, A203, EDP Sciences,
    2026, doi:<a href="https://doi.org/10.1051/0004-6361/202556032">10.1051/0004-6361/202556032</a>.
  short: C.L. Pollock, R. Gottumukkala, K.E. Heintz, G.B. Brammer, G. Roberts-Borsani,
    P.A. Oesch, J. Witstok, K.Z. Arellano-Córdova, F. Cullen, D. Scholte, C. Terp,
    L. Rowland, A. Sneppen, K. Ito, F. Valentino, J.J. Matthee, D. Watson, S. Toft,
    Astronomy &#38; Astrophysics 708 (2026).
das_tickbox: '0'
date_created: 2026-09-06T22:01:56Z
date_published: 2026-04-01T00:00:00Z
date_updated: 2026-09-09T12:07:45Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1051/0004-6361/202556032
external_id:
  arxiv:
  - '2506.15779'
file:
- access_level: open_access
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  content_type: application/pdf
  creator: dernst
  date_created: 2026-09-09T12:03:50Z
  date_updated: 2026-09-09T12:03:50Z
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file_date_updated: 2026-09-09T12:03:50Z
fulldoi: https://doi.org/10.1051/0004-6361/202556032
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: no
scopus_import: '1'
status: public
supplementarymaterial: no
title: Novel z ∼ 10 auroral line measurements extend the gradual offset of the fundamental
  metallicity relation deep into the first gigayear of cosmic time
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'
...