---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
PlanS_conform: '1'
_id: '21898'
abstract:
- lang: eng
  text: We investigate the nature and spectroscopic diversity of early galaxies from
    a sample of 41 sources at $z\geqslant 10$ with James Webb Space Telescope (JWST)/NIRSpec
    prism observations. We compare the properties of strong ultraviolet (UV) line
    emitters, traced by intense C iv emission, with those of more ‘typical’ sources
    with weak or undetected C iv. The more typical (or ‘C iv-weak’) sources reveal
    significant scatter in their C iii] line strengths, UV continuum slopes, and physical
    sizes, spanning C iii] equivalent widths (EWs) of $\sim$1–51 Å, UV slopes of $\beta
    \sim -1.6$ to $-2.6$, and half-light radii of $\sim$50–1000 pc. In contrast, C iv-strong
    sources occupy the tail of these distributions, with C iii] EWs of 16–51 Å, UV
    slopes $\beta \lesssim -2.5$, compact morphologies ($r_{\rm 50} \lesssim 100$ pc),
    and elevated star formation surface densities ($\Sigma _{\rm SFR} \gtrsim 100\,
    M_\odot \, \mathrm{yr}^{-1}\, \mathrm{kpc}^{-2}$). These properties suggest concentrated
    starbursts that temporarily outshine the host galaxy. Comparing average properties
    from composite spectra, we find the diversity of the sample is primarily driven
    by bursty star formation on very short time-scales ($\le$3 Myr), with strong C iv
    emitters observed at the apex of the bursts and sources devoid of emission lines
    during relative inactivity. An apparent association between strong C iv and enhanced
    nitrogen abundance suggests both may be modulated by the same duty cycle, reflecting
    a generic mode of star formation. We show that active galactic nuclei are unlikely
    to contribute significantly to this duty cycle based on UV line diagnostics and
    photoionization models. Our results support a picture whereby brief bursts and
    lulls can explain the spectral diversity and early growth of bright galaxies in
    the first 500 Myr.
acknowledgement: "We thank the anonymous referee for useful and constructive\r\nfeedback
  that improved the manuscript. GRB is grateful to Vasily\r\nBelokurov and Sarah Kane
  for providing the relevant abundances\r\nforthe Aurora data in Fig. 11, as well
  asto Tiger Yu-Yang Hsiao for\r\nhelpful discussions regarding the MACS 0647-JD source.
  We are\r\nalso grateful to Gabe Brammerfor useful discussions and his continuous
  efforts in maintaining and improving the msaexp code,\r\nfrom which the high-z community
  continues to benefit greatly.\r\nLastly, we also thank the numerous teams of the
  observational\r\nprograms used in this study, for developing these valuable data\r\nsets.
  The data used in this study are derived from the following\r\nprograms: 1181 (PI
  Eisenstein; D. J. Eisenstein et al. 2023a), 1210\r\n(PI Luetzgendorf; D. J. Eisenstein
  et al. 2023a), 1211 (PI Isaak;\r\nM. V. Maseda et al. 2024), 1286 (PI Luetzgendorf;
  D. J. Eisenstein\r\net al. 2023a), 1287 (PI Isaak; D. J. Eisenstein et al. 2023a),
  1345\r\n(PI Finkelstein; S. L. Finkelstein et al. 2025), 1433 (PI Coe; T. Y.-\r\nY.
  Hsiao et al. 2024a), 2561 (PI Labbé; R. Bezanson et al. 2022),\r\n2750 (PI Arrabal
  Haro; P. Arrabal Haro et al. 2023b), 3073 (PI\r\nCastellano; M. Castellano et al.
  2024), 3215 (PIs Eisenstein &\r\nMaiolino; D. J. Eisenstein et al. 2023b), 5224
  (PIs Oesch & Naidu;\r\nOesch et al. in preparation), 6368 (PI Dickinson; V. Kokorev
  et al.\r\n2025). The authors acknowledge the aforementioned teams and\r\nPIs where
  development of their observing program(s) was done\r\nwith a zero-exclusive-access
  period.\r\nThis work is based on observations made with the\r\nNASA/ESA/CSA JWST.
  The data were obtained from the\r\nMikulski Archive for Space Telescopes at the
  Space Telescope\r\nScience Institute, which is operated by the Association of\r\nUniversities
  for Research in Astronomy, Inc., under NASA\r\ncontract NAS 5-03127 for JWST. The
  specific observations\r\nanalysed can be accessed via DOI 10.17909/jqj3-ws37. Some\r\nof
  the data products presented herein were retrieved from the\r\nDawn JWST Archive
  (DJA). DJA is an initiative of the Cosmic\r\nDawn Center (DAWN), which is funded
  by the Danish National\r\nResearch Foundation under grant DNRF140.\r\nRSE acknowledges
  generous financial support from the Peter\r\nand Patricia Gruber Foundation. YF
  acknowledgessupportsfrom\r\nJSPS KAKENHI Grant Numbers JP22K21349 and JP23K13149.\r\nThis
  work has received funding from the Swiss State Secretariat\r\nfor Education, Research
  and Innovation (SERI) under contract\r\nnumber MB22.00072, as well as from the Swiss
  National Science\r\nFoundation (SNSF) through project grant 200020_207349."
article_number: stag701
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Guido
  full_name: Roberts-Borsani, Guido
  last_name: Roberts-Borsani
- first_name: Pascal A
  full_name: Oesch, Pascal A
  last_name: Oesch
- first_name: Richard
  full_name: Ellis, Richard
  last_name: Ellis
- first_name: Andrea
  full_name: Weibel, Andrea
  last_name: Weibel
- first_name: Emma
  full_name: Giovinazzo, Emma
  last_name: Giovinazzo
- first_name: Rychard
  full_name: Bouwens, Rychard
  last_name: Bouwens
- first_name: Pratika
  full_name: Dayal, Pratika
  last_name: Dayal
- first_name: Adriano
  full_name: Fontana, Adriano
  last_name: Fontana
- first_name: Kasper E
  full_name: Heintz, Kasper E
  last_name: Heintz
- first_name: Jorryt J
  full_name: Matthee, Jorryt J
  id: 7439a258-f3c0-11ec-9501-9df22fe06720
  last_name: Matthee
  orcid: 0000-0003-2871-127X
- first_name: Romain A
  full_name: Meyer, Romain A
  last_name: Meyer
- first_name: Laura
  full_name: Pentericci, Laura
  last_name: Pentericci
- first_name: Alice
  full_name: Shapley, Alice
  last_name: Shapley
- first_name: Sandro
  full_name: Tacchella, Sandro
  last_name: Tacchella
- first_name: Tommaso
  full_name: Treu, Tommaso
  last_name: Treu
- first_name: Fabian
  full_name: Walter, Fabian
  last_name: Walter
- first_name: Hakim
  full_name: Atek, Hakim
  last_name: Atek
- first_name: Sownak
  full_name: Bose, Sownak
  last_name: Bose
- first_name: Marco
  full_name: Castellano, Marco
  last_name: Castellano
- first_name: Yoshinobu
  full_name: Fudamoto, Yoshinobu
  last_name: Fudamoto
- first_name: Takahiro
  full_name: Morishita, Takahiro
  last_name: Morishita
- first_name: Rohan P
  full_name: Naidu, Rohan P
  last_name: Naidu
- first_name: Ryan L
  full_name: Sanders, Ryan L
  last_name: Sanders
- first_name: Arjen
  full_name: van der Wel, Arjen
  last_name: van der Wel
citation:
  ama: 'Roberts-Borsani G, Oesch PA, Ellis R, et al. JWST spectroscopic insights into
    the diversity of galaxies in the first 500 Myr: Short-lived snapshots along a
    common evolutionary pathway. <i>Monthly Notices of the Royal Astronomical Society</i>.
    2026;548(3). doi:<a href="https://doi.org/10.1093/mnras/stag701">10.1093/mnras/stag701</a>'
  apa: 'Roberts-Borsani, G., Oesch, P. A., Ellis, R., Weibel, A., Giovinazzo, E.,
    Bouwens, R., … van der Wel, A. (2026). JWST spectroscopic insights into the diversity
    of galaxies in the first 500 Myr: Short-lived snapshots along a common evolutionary
    pathway. <i>Monthly Notices of the Royal Astronomical Society</i>. Oxford University
    Press. <a href="https://doi.org/10.1093/mnras/stag701">https://doi.org/10.1093/mnras/stag701</a>'
  chicago: 'Roberts-Borsani, Guido, Pascal A Oesch, Richard Ellis, Andrea Weibel,
    Emma Giovinazzo, Rychard Bouwens, Pratika Dayal, et al. “JWST Spectroscopic Insights
    into the Diversity of Galaxies in the First 500 Myr: Short-Lived Snapshots along
    a Common Evolutionary Pathway.” <i>Monthly Notices of the Royal Astronomical Society</i>.
    Oxford University Press, 2026. <a href="https://doi.org/10.1093/mnras/stag701">https://doi.org/10.1093/mnras/stag701</a>.'
  ieee: 'G. Roberts-Borsani <i>et al.</i>, “JWST spectroscopic insights into the diversity
    of galaxies in the first 500 Myr: Short-lived snapshots along a common evolutionary
    pathway,” <i>Monthly Notices of the Royal Astronomical Society</i>, vol. 548,
    no. 3. Oxford University Press, 2026.'
  ista: 'Roberts-Borsani G, Oesch PA, Ellis R, Weibel A, Giovinazzo E, Bouwens R,
    Dayal P, Fontana A, Heintz KE, Matthee JJ, Meyer RA, Pentericci L, Shapley A,
    Tacchella S, Treu T, Walter F, Atek H, Bose S, Castellano M, Fudamoto Y, Morishita
    T, Naidu RP, Sanders RL, van der Wel A. 2026. JWST spectroscopic insights into
    the diversity of galaxies in the first 500 Myr: Short-lived snapshots along a
    common evolutionary pathway. Monthly Notices of the Royal Astronomical Society.
    548(3), stag701.'
  mla: 'Roberts-Borsani, Guido, et al. “JWST Spectroscopic Insights into the Diversity
    of Galaxies in the First 500 Myr: Short-Lived Snapshots along a Common Evolutionary
    Pathway.” <i>Monthly Notices of the Royal Astronomical Society</i>, vol. 548,
    no. 3, stag701, Oxford University Press, 2026, doi:<a href="https://doi.org/10.1093/mnras/stag701">10.1093/mnras/stag701</a>.'
  short: G. Roberts-Borsani, P.A. Oesch, R. Ellis, A. Weibel, E. Giovinazzo, R. Bouwens,
    P. Dayal, A. Fontana, K.E. Heintz, J.J. Matthee, R.A. Meyer, L. Pentericci, A.
    Shapley, S. Tacchella, T. Treu, F. Walter, H. Atek, S. Bose, M. Castellano, Y.
    Fudamoto, T. Morishita, R.P. Naidu, R.L. Sanders, A. van der Wel, Monthly Notices
    of the Royal Astronomical Society 548 (2026).
date_created: 2026-05-20T14:34:29Z
date_published: 2026-05-01T00:00:00Z
date_updated: 2026-05-21T06:16:04Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1093/mnras/stag701
external_id:
  arxiv:
  - '2508.21708'
file:
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has_accepted_license: '1'
intvolume: '       548'
issue: '3'
language:
- iso: eng
month: '05'
oa: 1
oa_version: Published Version
publication: Monthly Notices of the Royal Astronomical Society
publication_identifier:
  eissn:
  - 1365-2966
  issn:
  - 0035-8711
publication_status: published
publisher: Oxford University Press
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'JWST spectroscopic insights into the diversity of galaxies in the first 500
  Myr: Short-lived snapshots along a common evolutionary pathway'
tmp:
  image: /images/cc_by.png
  legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
  name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
  short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 548
year: '2026'
...