Abstract
We present the first James Webb Space Telescope/NIRCam-led determination of 7 < z < 9 galaxy properties based on broadband imaging from 0.8 to 5 μm as part of the GLASS-JWST Early Release Science program. This is the deepest data set acquired at these wavelengths to date, with an angular resolution ≲0.″14. We robustly identify 13 galaxies with signal-to-noise ratio ≳ 8 in F444W from 8 arcmin2 of data at m AB ≤ 28 from a combination of dropout and photometric redshift selection. From simulated data modeling, we estimate the dropout sample purity to be ≳90%. We find that the number density of these F444W-selected sources is broadly consistent with expectations from the UV luminosity function determined from Hubble Space Telescope data. We characterize galaxy physical properties using a Bayesian spectral energy distribution fitting method, finding a median stellar mass of 108.5 M ⊙ and age 140 Myr, indicating they started ionizing their surroundings at redshift z > 9.5. Their star formation main sequence is consistent with predictions from simulations. Lastly, we introduce an analytical framework to constrain main-sequence evolution at z > 7 based on galaxy ages and basic assumptions, through which we find results consistent with expectations from cosmological simulations. While this work only gives a glimpse of the properties of typical galaxies that are thought to drive the reionization of the universe, it clearly shows the potential of JWST to unveil unprecedented details of galaxy formation in the first billion years.
| Original language | English (US) |
|---|---|
| Article number | L26 |
| Journal | Astrophysical Journal Letters |
| Volume | 942 |
| Issue number | 2 |
| DOIs | |
| State | Published - Jan 1 2023 |
Bibliographical note
Funding Information:This work is based 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. These observations are associated with program JWST-ERS-1324. We acknowledge financial support from NASA through grants JWST-ERS-1324. This research is supported in part by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. K.G. and T.N. acknowledge support from the Australian Research Council Laureate Fellowship FL180100060. M.B. acknowledges support from the Slovenian national research agency ARRS through grant N1-0238.
Funding Information:
This work is based 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. These observations are associated with program JWST-ERS-1324. We acknowledge financial support from NASA through grants JWST-ERS-1324. This research is supported in part by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. K.G. and T.N. acknowledge support from the Australian Research Council Laureate Fellowship FL180100060. M.B. acknowledges support from the Slovenian national research agency ARRS through grant N1-0238.
Publisher Copyright:
© 2023. The Author(s). Published by the American Astronomical Society.