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 - Publisher Copyright:
© 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
PY - 2024
Y1 - 2024
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
U2 - 10.1093/mnras/stad3877
DO - 10.1093/mnras/stad3877
M3 - Journal 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 -