The Evolution of Half-Mass Radii and Color Gradients for Young and Old Quiescent Galaxies at $0.5 < z < 3$ with JWST/PRIMER

TL;DR

This study uses JWST imaging to analyze the size and color gradient evolution of quiescent galaxies from redshift 0.5 to 3, revealing that infrared sizes accurately trace mass and that size growth is driven by minor mergers and progenitor bias.

Contribution

It provides the first detailed comparison of half-mass and half-light radii across a wide redshift range using JWST data, highlighting the roles of progenitor bias and minor mergers in size evolution.

Findings

Infrared sizes closely match mass-weighted sizes.

Optical sizes are slightly larger than infrared sizes.

Size growth is consistent with minor mergers and progenitor bias.

Abstract

We present a study of the size growth of the red sequence between $0.5<z<3,$ tracing the evolution of quiescent galaxies in both effective half-light and half-mass radii using multi-wavelength JWST/NIRCam imaging provided by the PRIMER survey. Half-light radii are measured from imaging in 6 different filters for 455 quiescent galaxies with log($M_*/M_{\odot}$)$>10$, whereas half-mass radii are derived from the F444W profiles together with the F277W-F444W color-$M_*$/L relation. We investigate the dependence of the ratio $r_{e, \mathrm{mass}}/r_{e, \mathrm{light}}$ on redshift, stellar mass, and the wavelength used to measure $r_{e, \mathrm{light}}$, also separating the sample into younger and older quiescent galaxies. Our data demonstrate that rest-frame infrared sizes accurately trace mass-weighted sizes while sizes measured at rest-frame optical wavelengths (0.5-0.7$\mu$m) are 0.1-0.2 dex larger, with only minor variations in redshift. We find that the average size of young quiescent galaxies agrees with that of old quiescent galaxies at intermediate masses, $10<$log($M_*/M_{\odot}$)$<11$, within their respective uncertainties in all observed-frame half-light, rest-frame half-light and half-mass radius measurements. At face value, our results point to a combination of progenitor bias and minor mergers driving the size growth of intermediate-mass quiescent galaxies at $0.5<z<3$. Our results further indicate that the varying contributions to the general quiescent population by young and old quiescent galaxies can mimic evolution in redshift.