JWST+ALMA Reveal the Buildup of Stellar Mass in the Cores of Dusty Star-forming Galaxies at Cosmic Noon

Abstract Dusty star-forming galaxies (DSFGs) have long been suspected to serve as the missing evolutionary bridge between the star-forming and quiescent phases of massive galaxy evolution. With the combined power of JWST and the Atacama Large Millimeter/submillimeter Array (ALMA), it is now possible to use high-resolution imaging at rest-frame ultraviolet (UV), optical, near-infrared (NIR), and submillimeter wavelengths to study the multiwavelength morphologies tracing both the stellar populations and dust during this key phase. We present the joint analysis of JWST/NIRCam imaging in GOODS-S and millimeter dust emission traced by ALMA for a sample of 33 galaxies at z = 1.5–5.5 selected from the 1.1 mm GOODS-ALMA 2.0 survey, and compare the morphologies of this population to mass- and redshift-selected samples of field star-forming and quiescent galaxies. The 1.1 mm selected sample is morphologically distinct from other similarly massive star-forming galaxies; we find a steeper size-wavelength gradient from 1.5 to 4.4 μ m, with a more dramatic decrease in size toward longer wavelengths. While the rest-NIR surface brightness profiles of the 1.1 mm selected galaxies are brighter in the inner regions relative to the field star-forming population, they are remarkably similar to the quiescent population. These morphological differences could suggest that DSFGs, unlike more typical star-forming galaxies, have already built up stellar mass in a severely dust-obscured core, leading to extended and clumpy morphologies at rest-UV and rest-optical wavelengths and more compact emission in the rest-NIR that is co-spatial with dust. If the bulge is already established, we speculate that millimeter-selected galaxies may imminently evolve to join their quiescent descendants.