Optically Invisible Galaxies at Cosmic Noon and beyond with JWST/UNCOVER

Abstract

The traditional selection bias in high-redshift galaxy surveys toward rest-frame ultraviolet emission has constrained our understanding of the high-redshift universe by systematically excluding optically faint (observer-frame) galaxies. Utilising JWST UNCOVER and MegaScience data of the Abell 2744 cluster field, we identify 113 high-redshift ($z>2$) and 94 low-redshift ($z<2$) HST-dark galaxies using a red $1.50-3.56\mu$m color criterion. Their physical properties were derived using multiwavelength photometry from 20 JWST/NIRCam and 7 HST filters. Unlike classical submillimeter and \textit{Spitzer}-selected HST-dark galaxies that primarily identify the most massive, dusty, highly star-forming galaxies, our study uncovers a moderately dusty population across a significantly broader range of stellar mass and star-formation rate. Leveraging gravitational magnification and ultra-deep JWST imaging, we found HST-dark galaxies with a stellar mass as low as $10^{7.5}$ at $z>2$. These galaxies have smaller sizes and follow the star-forming main sequence. Our analysis reveals a prominent peak in the Star Formation Rate Density at $z\approx 4.5$ ($9.89_{-4.34}^{+6.93}\times 10^{-3}{M}_{\odot }{\text{yr}}^{-1}{\text{Mpc}}^{-3}$). We also characterise a sub-population at $z<2$ of Highly Extincted Low-Mass analogues with extremely low stellar masses (median $\log M_{\star }/M_{\odot }\approx 7.10$) and high dust extinction (median $A_V\approx 1.97$ mag). Our sample demonstrates the unique power of JWST to reveal this previously missing galaxy population and to provide a more complete census of galaxies in the high-z universe.

21 pages, 12 figures, 8 tables. Submitted to ApJ