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

We present the UV-to-near-IR (NIR) size evolution of a sample of 161 quiescent galaxies with M* > 1010 M⊙over 0.5 < z < 5. With deep multiband NIRCam images in GOODS-South from JADES, we measure the effective radii (Re) of the galaxies at rest-frame 0.3, 0.5, and 1 μm. On average, we find that quiescent galaxies are 45% (15%) more compact at rest-frame 1 μm than they are at 0.3 μm (0.5 μm). Regardless of wavelengths, the Re of quiescent galaxies strongly evolves with redshift, and this evolution depends on stellar mass. For lower-mass quiescent galaxies with M* = 1010–1010.6 M⊙, the evolution follows Re ∝ (1 + z)−1.1, whereas it becomes steeper, following Re ∝ (1 + z)−1.7, for higher-mass quiescent galaxies with M* > 1010.6 M⊙. To constrain the physical mechanisms driving the apparent size evolution, we study the relationship between Re and the formation redshift (zform) of quiescent galaxies. For lower-mass quiescent galaxies, this relationship is broadly consistent with Re∝(1+zform)−1 , in line with the expectation of the progenitor effect. For higher-mass quiescent galaxies, the relationship between Re and zform depends on stellar age. Older quiescent galaxies have a steeper relationship between Re and zform 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 Σe ≳ 1010 M⊙ kpc−2, and their Re 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 zspec ∼ 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.