---
DOAJ_listed: '1'
_id: '17234'
abstract:
- lang: eng
  text: The identification of red, apparently massive galaxies at z > 7 in early James
    Webb Space Telescope (JWST) photometry suggests a strongly accelerated time line
    compared to standard models of galaxy growth. A major uncertainty in the interpretation
    is whether the red colors are caused by evolved stellar populations, dust, or
    other effects such as emission lines or active galactic nuclei (AGNs). Here we
    show that three of the massive galaxy candidates at z = 6.7–8.4 have prominent
    Balmer breaks in JWST/NIRSpec spectroscopy from the RUBIES program. The Balmer
    breaks demonstrate unambiguously that stellar emission dominates at λrest = 0.4
    μm and require formation histories extending hundreds of millions of years into
    the past in galaxies only 600–800 Myr after the big bang. Two of the three galaxies
    also show broad Balmer lines, with Hβ FWHM > 2500 km s−1, suggesting that dust-reddened
    AGNs contribute to, or even dominate, the spectral energy distributions of these
    galaxies at λrest ≳ 0.6 μm. All three galaxies have relatively narrow [O iii]
    lines, seemingly ruling out a high-mass interpretation if the lines arise in dynamically
    relaxed, inclined disks. Yet the inferred masses also remain highly uncertain.
    We model the high-quality spectra using Prospector to decompose the continuum
    into stellar and AGN components and explore limiting cases in stellar/AGN contribution.
    This produces a wide range of possible stellar masses, spanning M⋆ ∼ 109−1011M⊙.
    Nevertheless, all fits suggest a very early and rapid formation, most of which
    follow with a truncation in star formation. Potential origins and evolutionary
    tracks for these objects are discussed, from the cores of massive galaxies to
    low-mass galaxies with overmassive black holes. Intriguingly, we find all of these
    explanations to be incomplete; deeper and redder data are needed to understand
    the physics of these systems.
acknowledgement: "We thank the anonymous referee for the helpful comments. B.W. and
  J.L. acknowledge support from JWST-GO04233.009-A. The Cosmic Dawn Center is funded
  by the Danish National Research Foundation (DNRF) under grant No. 140. This research
  was supported by the International Space Science Institute (ISSI) in Bern, through
  ISSI International Team project No. 562 (First Light at Cosmic Dawn: Exploiting
  the James Webb Space Telescope Revolution). 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. The JWST data presented in this
  Letter 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:10.17909/3a4n-9p88. Computations for this research were performed on the
  Pennsylvania State University’s Institute for Computational and Data Sciences’ Roar
  supercomputer. This publication made use of the NASA Astrophysical Data System for
  bibliographic information. \r\nFacilities: HST (ACS, WFC3), JWST (NIRCam, NIRSpec).
  Software: Astropy (Astropy Collaboration et al. 2013, 2018, 2022), dynesty (Speagle
  2020), EAzY (Brammer et al. 2008),\r\nemcee (Foreman-Mackey et al. 2013), Matplotlib
  (Hunter 2007), msaexp (Brammer 2023b), msafit (de Graaff et al. 2024a), NumPy (Harris
  et al. 2020), Prospector (Johnson et al. 2021), Python-FSPS (Johnson et al. 2023)."
article_number: L13
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Bingjie
  full_name: Wang, Bingjie
  last_name: Wang
- first_name: Joel
  full_name: Leja, Joel
  last_name: Leja
- first_name: Anna
  full_name: De Graaff, Anna
  last_name: De Graaff
- first_name: Gabriel B.
  full_name: Brammer, Gabriel B.
  last_name: Brammer
- first_name: Andrea
  full_name: Weibel, Andrea
  last_name: Weibel
- first_name: Pieter
  full_name: Van Dokkum, Pieter
  last_name: Van Dokkum
- first_name: Josephine F.W.
  full_name: Baggen, Josephine F.W.
  last_name: Baggen
- first_name: Katherine A.
  full_name: Suess, Katherine A.
  last_name: Suess
- first_name: Jenny E.
  full_name: Greene, Jenny E.
  last_name: Greene
- first_name: Rachel
  full_name: Bezanson, Rachel
  last_name: Bezanson
- first_name: Nikko J.
  full_name: Cleri, Nikko J.
  last_name: Cleri
- first_name: Michaela
  full_name: Hirschmann, Michaela
  last_name: Hirschmann
- first_name: Ivo
  full_name: Labbé, Ivo
  last_name: Labbé
- first_name: Jorryt J
  full_name: Matthee, Jorryt J
  id: 7439a258-f3c0-11ec-9501-9df22fe06720
  last_name: Matthee
  orcid: 0000-0003-2871-127X
- first_name: Ian
  full_name: Mcconachie, Ian
  last_name: Mcconachie
- first_name: Rohan P.
  full_name: Naidu, Rohan P.
  last_name: Naidu
- first_name: Erica
  full_name: Nelson, Erica
  last_name: Nelson
- first_name: Pascal A.
  full_name: Oesch, Pascal A.
  last_name: Oesch
- first_name: David J.
  full_name: Setton, David J.
  last_name: Setton
- first_name: Christina C.
  full_name: Williams, Christina C.
  last_name: Williams
citation:
  ama: 'Wang B, Leja J, De Graaff A, et al. RUBIES: Evolved stellar populations with
    extended formation histories at z ∼ 7-8 in candidate massive galaxies identified
    with JWST/NIRSpec. <i>Astrophysical Journal Letters</i>. 2024;969(1). doi:<a href="https://doi.org/10.3847/2041-8213/ad55f7">10.3847/2041-8213/ad55f7</a>'
  apa: 'Wang, B., Leja, J., De Graaff, A., Brammer, G. B., Weibel, A., Van Dokkum,
    P., … Williams, C. C. (2024). RUBIES: Evolved stellar populations with extended
    formation histories at z ∼ 7-8 in candidate massive galaxies identified with JWST/NIRSpec.
    <i>Astrophysical Journal Letters</i>. IOP Publishing. <a href="https://doi.org/10.3847/2041-8213/ad55f7">https://doi.org/10.3847/2041-8213/ad55f7</a>'
  chicago: 'Wang, Bingjie, Joel Leja, Anna De Graaff, Gabriel B. Brammer, Andrea Weibel,
    Pieter Van Dokkum, Josephine F.W. Baggen, et al. “RUBIES: Evolved Stellar Populations
    with Extended Formation Histories at z ∼ 7-8 in Candidate Massive Galaxies Identified
    with JWST/NIRSpec.” <i>Astrophysical Journal Letters</i>. IOP Publishing, 2024.
    <a href="https://doi.org/10.3847/2041-8213/ad55f7">https://doi.org/10.3847/2041-8213/ad55f7</a>.'
  ieee: 'B. Wang <i>et al.</i>, “RUBIES: Evolved stellar populations with extended
    formation histories at z ∼ 7-8 in candidate massive galaxies identified with JWST/NIRSpec,”
    <i>Astrophysical Journal Letters</i>, vol. 969, no. 1. IOP Publishing, 2024.'
  ista: 'Wang B, Leja J, De Graaff A, Brammer GB, Weibel A, Van Dokkum P, Baggen JFW,
    Suess KA, Greene JE, Bezanson R, Cleri NJ, Hirschmann M, Labbé I, Matthee JJ,
    Mcconachie I, Naidu RP, Nelson E, Oesch PA, Setton DJ, Williams CC. 2024. RUBIES:
    Evolved stellar populations with extended formation histories at z ∼ 7-8 in candidate
    massive galaxies identified with JWST/NIRSpec. Astrophysical Journal Letters.
    969(1), L13.'
  mla: 'Wang, Bingjie, et al. “RUBIES: Evolved Stellar Populations with Extended Formation
    Histories at z ∼ 7-8 in Candidate Massive Galaxies Identified with JWST/NIRSpec.”
    <i>Astrophysical Journal Letters</i>, vol. 969, no. 1, L13, IOP Publishing, 2024,
    doi:<a href="https://doi.org/10.3847/2041-8213/ad55f7">10.3847/2041-8213/ad55f7</a>.'
  short: B. Wang, J. Leja, A. De Graaff, G.B. Brammer, A. Weibel, P. Van Dokkum, J.F.W.
    Baggen, K.A. Suess, J.E. Greene, R. Bezanson, N.J. Cleri, M. Hirschmann, I. Labbé,
    J.J. Matthee, I. Mcconachie, R.P. Naidu, E. Nelson, P.A. Oesch, D.J. Setton, C.C.
    Williams, Astrophysical Journal Letters 969 (2024).
date_created: 2024-07-14T22:01:11Z
date_published: 2024-07-01T00:00:00Z
date_updated: 2025-09-08T08:10:21Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.3847/2041-8213/ad55f7
external_id:
  arxiv:
  - '2405.01473'
  isi:
  - '001257903200001'
file:
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  date_created: 2024-07-16T06:24:29Z
  date_updated: 2024-07-16T06:24:29Z
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has_accepted_license: '1'
intvolume: '       969'
isi: 1
issue: '1'
language:
- iso: eng
month: '07'
oa: 1
oa_version: Published Version
publication: Astrophysical Journal Letters
publication_identifier:
  eissn:
  - 2041-8213
  issn:
  - 2041-8205
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'RUBIES: Evolved stellar populations with extended formation histories at z
  ∼ 7-8 in candidate massive galaxies identified with JWST/NIRSpec'
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: 317138e5-6ab7-11ef-aa6d-ffef3953e345
volume: 969
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