TY - JOUR
T1 - EPOCHS IX. When cosmic dawn breaks
T2 - Evidence for evolved stellar populations in 7 < z < 12 galaxies from PEARLS GTO and public NIRCam imaging
AU - Trussler, James A.A.
AU - Conselice, Christopher J.
AU - Adams, Nathan
AU - Austin, Duncan
AU - Ferreira, Leonardo
AU - Harvey, Tom
AU - Li, Qiong
AU - Vijayan, Aswin P.
AU - Wilkins, Stephen M.
AU - Windhorst, Rogier A.
AU - Bhatawdekar, Rachana
AU - Cheng, Cheng
AU - Coe, Dan
AU - Cohen, Seth H.
AU - Driver, Simon P.
AU - Frye, Brenda
AU - Grogin, Norman A.
AU - Hathi, Nimish
AU - Jansen, Rolf A.
AU - Koekemoer, Anton
AU - Marshall, Madeline A.
AU - Nonino, Mario
AU - Ortiz, Rafael
AU - Pirzkal, Nor
AU - Robotham, Aaron
AU - Ryan, Russell E.
AU - D'Silva, Jordan C.J.
AU - Summers, Jake
AU - Tompkins, Scott
AU - Willmer, Christopher N.A.
AU - Yan, Haojing
N1 - Funding Information:
We dedicate this paper to the memory of our dear PEARLS colleague Mario Nonino, who was a gifted and dedicated scientist, and a generous person. We thank the referee for their useful comments which helped to improve this article. JT, CC, NA, and QL acknowledge support from the ERC Advanced Investigator Grant EPOCHS (788113). DA and TH acknowledge support from STFC in the form of PhD studentships. LF acknowledges financial support from Coordenação de Aperfeiçamento de Pessoal de Nível Superior – Brazil (CAPES) in the form of a PhD studentship. RW, SC, and RJ acknowledge support from NASA JWST Interdisciplinary Scientist grants NAG5 12460, NNX14AN10G, and 80NSSC18K0200 from GSFC. MAM acknowledges the support of a National Research Council of Canada Plaskett Fellowship, and the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE17010001. CNAW acknowledges funding from the JWST/NIRCam contract NASS-0215 to the University of Arizona, as well as support from the NIRCam Development contract NAS5-02105 from NASA Goddard Space Flight Center to the University of Arizona. MN acknowledges INAF-Mainstreams 1.05.01.86.20. APV acknowledges support from the Carlsberg Foundation (grant no. CF20-0534). The Cosmic Dawn Center (DAWN) is funded by the Danish National Research Foundation under grant no. 140.
Publisher Copyright:
© 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
PY - 2024/2
Y1 - 2024/2
N2 - The presence of evolved stars in high-redshift galaxies can place valuable indirect constraints on the onset of star formation in the Universe. Thus, we use PEARLS GTO (Prime Extragalactic Areas for Reionization and Lensing Science Guaranteed Time Observations) and public NIRCam (Near Infrared Camera) photometric data to search for Balmer-break candidate galaxies at 7 < z < 12. We find that our Balmer-break candidates at z ∼10.5 tend to be older (115 Myr), have lower inferred [O iii] + Hβ equivalent widths (120 Å), have lower specific star formation rates (6 Gyr-1) and redder UV slopes (β =-1.8) than our control sample of galaxies. However, these trends all become less strong at z ∼8, where the F444W filter now probes the strong rest-frame optical emission lines, thus providing additional constraints on the current star formation activity of these galaxies. Indeed, the bursty nature of epoch of reionization galaxies can lead to a disconnect between their current spectral energy distribution (SED) profiles and their more extended star formation histories. We discuss how strong emission lines, the cumulative effect of weak emission lines, dusty continua, and active galactic nuclei can all contribute to the photometric excess seen in the rest-frame optical, thus mimicking the signature of a Balmer break. Additional medium-band imaging will thus be essential to more robustly identify Balmer-break galaxies. However, the Balmer break alone cannot serve as a definitive proxy for the stellar age of galaxies, being complexly dependent on the star formation history. Ultimately, deep Near Infrared Spectrograph (NIRSpec) continuum spectroscopy and Mid-Infrared Instrument (MIRI) imaging will provide the strongest indirect constraints on the formation era of the first galaxies in the Universe, thereby revealing when cosmic dawn breaks.
AB - The presence of evolved stars in high-redshift galaxies can place valuable indirect constraints on the onset of star formation in the Universe. Thus, we use PEARLS GTO (Prime Extragalactic Areas for Reionization and Lensing Science Guaranteed Time Observations) and public NIRCam (Near Infrared Camera) photometric data to search for Balmer-break candidate galaxies at 7 < z < 12. We find that our Balmer-break candidates at z ∼10.5 tend to be older (115 Myr), have lower inferred [O iii] + Hβ equivalent widths (120 Å), have lower specific star formation rates (6 Gyr-1) and redder UV slopes (β =-1.8) than our control sample of galaxies. However, these trends all become less strong at z ∼8, where the F444W filter now probes the strong rest-frame optical emission lines, thus providing additional constraints on the current star formation activity of these galaxies. Indeed, the bursty nature of epoch of reionization galaxies can lead to a disconnect between their current spectral energy distribution (SED) profiles and their more extended star formation histories. We discuss how strong emission lines, the cumulative effect of weak emission lines, dusty continua, and active galactic nuclei can all contribute to the photometric excess seen in the rest-frame optical, thus mimicking the signature of a Balmer break. Additional medium-band imaging will thus be essential to more robustly identify Balmer-break galaxies. However, the Balmer break alone cannot serve as a definitive proxy for the stellar age of galaxies, being complexly dependent on the star formation history. Ultimately, deep Near Infrared Spectrograph (NIRSpec) continuum spectroscopy and Mid-Infrared Instrument (MIRI) imaging will provide the strongest indirect constraints on the formation era of the first galaxies in the Universe, thereby revealing when cosmic dawn breaks.
KW - galaxies: evolution
KW - galaxies: formation
KW - galaxies: high-redshift
KW - galaxies: star formation
UR - http://www.scopus.com/inward/record.url?scp=85182916656&partnerID=8YFLogxK
U2 - 10.1093/mnras/stad3877
DO - 10.1093/mnras/stad3877
M3 - Article
AN - SCOPUS:85182916656
SN - 0035-8711
VL - 527
SP - 11627
EP - 11650
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 4
ER -