JWST's PEARLS: A JWST/NIRCam view of ALMA sources

TL;DR

This study uses JWST/NIRCam to observe 19 ALMA-detected (sub)millimeter sources, revealing their properties, morphologies, and star formation activities, and providing insights into galaxy assembly at redshifts 1 to 4.5.

Contribution

First large sample of ALMA sources with JWST/NIRCam imaging, enabling detailed analysis of their properties and morphologies at high redshift.

Findings

Most sources are disk-like with little disturbance.

Sources have a wide range of star formation rates, including quiescent and actively star-forming.

Majority have small disks with median half-mass radius of 1.6 kpc.

Abstract

We report the results of James Webb Space Telescope/NIRCam observations of 19 (sub)millimeter (submm/mm) sources detected by the Atacama Large Millimeter Array (ALMA). The accurate ALMA positions allowed unambiguous identifications of their NIRCam counterparts. Taking gravitational lensing into account, these represent 16 distinct galaxies in three fields and constitute the largest sample of its kind to date. The counterparts' spectral energy distributions from rest-frame ultraviolet to near infrared provide photometric redshifts ($1<z<4.5$) and stellar masses ($M_*>10^{10.5}$ Msol), which are similar to sub-millimeter galaxy (SMG) hosts studied previously. However, our sample is fainter in submm/mm than the classic SMG samples are, and our sources exhibit a wider range of properties. They have dust-embedded star-formation rates as low as 10 Msol yr$^{-1}$, and the sources populate both the star-forming main sequence and the quiescent categories. The deep NIRCam data allow us to study the rest-frame near-IR morphologies. Excluding two multiply imaged systems and one quasar, the majority of the remaining sources are disk-like and show either little or no disturbance. This suggests that secular growth is a potential route for the assembly of high-mass disk galaxies. While a few hosts have large disks, the majority have small disks (median half-mass radius of 1.6 kpc). At this time, it is unclear whether this is due to the prevalence of small disks at these redshifts or some unknown selection effects of deep ALMA observations. A larger sample of ALMA sources with NIRCam observations will be able to address this question.