TY - JOUR
T1 - The star-forming and ionizing properties of dwarf z ~ 6–9 galaxies in JADES: insights on bursty star formation and ionized bubble growth
AU - Endsley, Ryan
AU - Stark, Daniel P
AU - Whitler, Lily
AU - Topping, Michael W
AU - Johnson, Benjamin D
AU - Robertson, Brant
AU - Tacchella, Sandro
AU - Alberts, Stacey
AU - Baker, William M
AU - Bhatawdekar, Rachana
AU - Boyett, Kristan
AU - Bunker, Andrew J
AU - Cameron, Alex J
AU - Carniani, Stefano
AU - Charlot, Stephane
AU - Chen, Zuyi
AU - Chevallard, Jacopo
AU - Curtis-Lake, Emma
AU - Danhaive, A Lola
AU - Egami, Eiichi
AU - Eisenstein, Daniel J
AU - Hainline, Kevin
AU - Helton, Jakob M
AU - Ji, Zhiyuan
AU - Looser, Tobias J
AU - Maiolino, Roberto
AU - Nelson, Erica
AU - Puskás, Dávid
AU - Rieke, George
AU - Rieke, Marcia
AU - Rix, Hans-Walter
AU - Sandles, Lester
AU - Saxena, Aayush
AU - Simmonds, Charlotte
AU - Smit, Renske
AU - Sun, Fengwu
AU - Williams, Christina C
AU - Willmer, Christopher N A
AU - Willott, Chris
AU - Witstok, Joris
N1 - © 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an open access article distributed under the Creative Commons Attribution License, to view a copy of the license, see: https://creativecommons.org/licenses/by/4.0/
PY - 2024/8/1
Y1 - 2024/8/1
N2 - Reionization is thought to be driven by faint star-forming galaxies, but characterizing this population has long remained very challenging. Here, we utilize deep nine-band JADES (JWST Advanced Deep Extragalactic Survey)/NIRCam (Near-Infrared Camera) imaging to study the star-forming and ionizing properties of 756 $z\sim 6-9$ galaxies, including hundreds of very ultraviolet (UV)-faint objects ($M_\mathrm{UV}\gt -18$). The faintest ($m\sim 30$) galaxies in our sample typically have stellar masses of $M_\ast \sim (1-3)\times 10^7\ \mathrm{ M}_\odot$ and young light-weighted ages ($\sim$50 Myr), though some show strong Balmer breaks implying much older ages ($\sim$500 Myr). We find no evidence for extremely massive galaxies ($\gt 3\times 10^{10}\ \mathrm{ M}_\odot$) in our sample. We infer a strong (factor $\gt $2) decline in the typical [O iii]$+$H $\beta$ equivalent widths (EWs) towards very faint $z\sim 6-9$ galaxies, yet a weak UV luminosity dependence on the H $\alpha$ EWs at $z\sim 6$. We demonstrate that these EW trends can be explained if fainter galaxies have systematically lower metallicities as well as more recently declining star formation histories relative to the most UV-luminous galaxies. Our data provide evidence that the brightest galaxies are frequently experiencing a recent strong upturn in star formation rate. We also discuss how the EW trends may be influenced by a strong correlation between $M_\mathrm{UV}$ and Lyman continuum escape fraction. This alternative explanation has dramatically different implications for the contribution of galaxies along the luminosity function to cosmic reionization. Finally, we quantify the photometric overdensities around two $z\,\gt\,7$ strong Ly $\alpha$ emitters. One Ly $\alpha$ emitter lies close to a strong photometric overdensity, while the other shows no significant nearby overdensity, perhaps implying that not all strong $z\,\gt\, 7$ Ly $\alpha$ emitters reside in large ionized bubbles.
AB - Reionization is thought to be driven by faint star-forming galaxies, but characterizing this population has long remained very challenging. Here, we utilize deep nine-band JADES (JWST Advanced Deep Extragalactic Survey)/NIRCam (Near-Infrared Camera) imaging to study the star-forming and ionizing properties of 756 $z\sim 6-9$ galaxies, including hundreds of very ultraviolet (UV)-faint objects ($M_\mathrm{UV}\gt -18$). The faintest ($m\sim 30$) galaxies in our sample typically have stellar masses of $M_\ast \sim (1-3)\times 10^7\ \mathrm{ M}_\odot$ and young light-weighted ages ($\sim$50 Myr), though some show strong Balmer breaks implying much older ages ($\sim$500 Myr). We find no evidence for extremely massive galaxies ($\gt 3\times 10^{10}\ \mathrm{ M}_\odot$) in our sample. We infer a strong (factor $\gt $2) decline in the typical [O iii]$+$H $\beta$ equivalent widths (EWs) towards very faint $z\sim 6-9$ galaxies, yet a weak UV luminosity dependence on the H $\alpha$ EWs at $z\sim 6$. We demonstrate that these EW trends can be explained if fainter galaxies have systematically lower metallicities as well as more recently declining star formation histories relative to the most UV-luminous galaxies. Our data provide evidence that the brightest galaxies are frequently experiencing a recent strong upturn in star formation rate. We also discuss how the EW trends may be influenced by a strong correlation between $M_\mathrm{UV}$ and Lyman continuum escape fraction. This alternative explanation has dramatically different implications for the contribution of galaxies along the luminosity function to cosmic reionization. Finally, we quantify the photometric overdensities around two $z\,\gt\,7$ strong Ly $\alpha$ emitters. One Ly $\alpha$ emitter lies close to a strong photometric overdensity, while the other shows no significant nearby overdensity, perhaps implying that not all strong $z\,\gt\, 7$ Ly $\alpha$ emitters reside in large ionized bubbles.
U2 - 10.1093/mnras/stae1857
DO - 10.1093/mnras/stae1857
M3 - Article
SN - 0035-8711
VL - 533
SP - 1111
EP - 1142
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 1
ER -