Size–Stellar Mass Relation and Morphology of Quiescent Galaxies at z ≥ 3 in Public JWST Fields

Abstract

We present the results of a systematic study of the rest-frame optical morphology of quiescent galaxies at z ≥ 3 using the Near-Infrared Camera (NIRCam) on board the James Webb Space Telescope (JWST). Based on a sample selected by UVJ color or NUVUVJ color, we focus on 26 quiescent galaxies with 9.8 < 11.4 at 2.8 < z phot < 4.6 with publicly available JWST data. Their sizes are constrained by fitting the Sérsic profile to all available NIRCam images. We see a negative correlation between the observed wavelength and the size and derive their size at the rest frame 0.5 μ m using size measurements in multiple bands. Our quiescent galaxies show a significant correlation between the rest-frame 0.5 μ m size and the stellar mass at z ≥ 3. The analytical fit for them at log ( M ⋆ / M ⊙ ) > 10.3 implies that our size–stellar mass relations are below those at lower redshifts, with the amplitude of ∼0.6 kpc at M ⋆ = 5 × 10 10 M ⊙ . This value agrees with the extrapolation of the size evolution of quiescent galaxies at z < 3 in the literature, implying that the size of quiescent galaxies increases monotonically from z ∼ 3–5. Our sample mainly comprises galaxies with bulge-like structures according to their median Sérsic index and axis ratio of n ∼ 3–4 and q ∼ 0.6–0.8, respectively. On the other hand, there is a trend of increasing fraction of galaxies with low Sérsic index at higher redshift, suggesting 3 < z < 5 might be the epoch of onset of morphological transformation with a fraction of very notable disky quenched galaxies.