The abundance of $z \gtrsim 10$ galaxy candidates in the HUDF using deep JWST NIRCam medium-band imaging

TL;DR

Using JWST NIRCam medium-band imaging, we identified and confirmed multiple galaxy candidates at redshifts greater than 10 in the HUDF, providing insights into early galaxy formation and the cosmic star-formation history.

Contribution

This study presents the first robust detection and spectroscopic confirmation of multiple $z geq 10$ galaxy candidates using JWST medium-band imaging, including a secure $z=11.6$ galaxy.

Findings

Detection of 6 robust high-redshift galaxy candidates.

Confirmation of a $z=11.6$ galaxy with secure photometric redshift.

Consistency of these galaxies with the UV luminosity function and star-formation rate density at $z oughly 11$.

Abstract

We utilise JWST NIRCam medium-band imaging to search for extreme redshift ($z \geq 9.5$) galaxy candidates in the Hubble Ultra Deep Field (HUDF) and the additional pointing within the GOODS-South field provided by the second NIRCam module. Our search reveals 6 robust candidates, 3 of which have recently been spectroscopically confirmed. One of these 3 is the previously controversial $z \simeq 12$ galaxy candidate UDF-22980 which is now detected in five JWST NIRCam medium-band filters (F182M, F210M, F430M, F460M and F480M), efficiently excluding alternative low-redshift solutions and allowing us to now report a secure photometric redshift of $z = 11.6 \pm 0.2$. We also detect 2 galaxies at $z \geq 12.5$ including a newly-detected candidate in the imaging provided by the second NIRCam module (south-west of the HUDF) at $z = 12.6 \pm 0.6$. We determine the physical properties of the 6 galaxies by fitting the 14-band photometry with Bagpipes. We find stellar masses of $\log(M_{\star}/{\rm {M_{\odot}}}) \simeq 7.5 - 8.7$ and star-formation rates of $\log(\rm{SFR}/M_{\odot}^{-1} \rm{yr}^{-1}) \simeq 0.3 - 5.0$. Despite the relatively small cosmological volume covered by the HUDF itself and the second NIRCam module imaging, we find that the existence of these galaxies is fully consistent with the latest measurements of both the UV luminosity function and cosmic star-formation rate density at $z\simeq11$, supporting a gradual steady decline in the cosmic star-formation rate density out to at least $z\simeq15$.