Abstract
We present a sample of low-mass quiescent galaxy sizes measured from the JWST PRIMER and UNCOVER treasury surveys using NIRCam imaging. A conservative sample of robust low-mass quiescent galaxy candidates is selected using rest-frame UVJ colors and specific star formation rate selections. We examine galaxies in both F150W and F444W, as F150W provides higher spatial resolution while F444W observes wavelengths that better trace the stellar mass. Sizes are fit in both bands using 2D-Sérsic modeling with GALFIT. With the impressive spatial resolution afforded by JWST, we confirm an unambiguous flattening of the quiescent size-mass relation in both filters at the low-mass end. These low-mass quenched galaxies have more disk-like morphologies compared to the high Sérsic indices measured in their high-mass counterparts. The flattening, as well as the transition to steep size growth at log(M/Msun)~10-10.5, is potentially evidence for a distinct transition between mass-driven quenching and other mechanisms, such as environmentally-driven quenching. Alternatively, this change in the slope of the quiescent size-mass relation could indicate a shift from size growth due to star formation to size growth via mergers or a fundamental limitation on the allowed density of galaxies.
