JADES: Rest-frame UV-to-NIR Size Evolution of Massive Quiescent Galaxies from Redshift z = 5 to z = 0.5

Abstract We present the UV-to-near-IR (NIR) size evolution of a sample of 161 quiescent galaxies with M * > 10 10 M ⊙ over 0.5 < z < 5. With deep multiband NIRCam images in GOODS-South from JADES, we measure the effective radii ( R e ) of the galaxies at rest-frame 0.3, 0.5, and 1 μ m. On average, we find that quiescent galaxies are 45% (15%) more compact at rest-frame 1 μ m than they are at 0.3 μ m (0.5 μ m). Regardless of wavelengths, the R e of quiescent galaxies strongly evolves with redshift, and this evolution depends on stellar mass. For lower-mass quiescent galaxies with M * = 10 10 –10 10.6 M ⊙ , the evolution follows R e ∝ (1 + z ) −1.1 , whereas it becomes steeper, following R e ∝ (1 + z ) −1.7 , for higher-mass quiescent galaxies with M * > 10 10.6 M ⊙ . To constrain the physical mechanisms driving the apparent size evolution, we study the relationship between R e and the formation redshift ( z form ) of quiescent galaxies. For lower-mass quiescent galaxies, this relationship is broadly consistent with R e ∝ ( 1 + z form ) − 1 , in line with the expectation of the progenitor effect. For higher-mass quiescent galaxies, the relationship between R e and z form depends on stellar age. Older quiescent galaxies have a steeper relationship between R e and z form than that expected from the progenitor effect alone, suggesting that mergers and/or post-quenching continuous gas accretion drive additional size growth in very massive systems. We find that the z > 3 quiescent galaxies in our sample are very compact, with mass surface densities Σ e ≳ 10 10 M ⊙ kpc −2 , and their R e are possibly even smaller than anticipated from the size evolution measured for lower-redshift quiescent galaxies. Finally, we take a close look at the structure of GS-9209, one of the earliest confirmed massive quiescent galaxies at z spec ∼ 4.7. From UV to NIR, GS-9209 becomes increasingly compact, and its light profile becomes more spheroidal, showing that the color gradient is already present in this earliest massive quiescent galaxy.