Early results from GLASS-JWST XIV: A first morphological atlas of the 1 < z < 5 Universe in the rest-frame optical

Abstract

We present a rest-frame optical morphological analysis of galaxies observed with the NIRCam imager on the James Webb Space Telescope (JWST) as part of the GLASS-JWST Early Release Science program. We select 388 sources at redshifts \(0.8 < z < 5.4\) and use the seven 0.9--5\micron\ NIRCam filters to generate rest-frame $gri$ composite color images, and conduct visual morphological classification. Compared to HST-based work we find a higher incidence of disks and bulges than expected at $z>1.5$, revealed by rest frame optical imaging. We detect 123 clear disks (58 at $z>1.5$) of which 76 have bulges. No evolution of bulge fraction with redshift is evident: 61\% at \(z<2\) (\(N=110\)) versus 60\% at \(z\geq2\) (\(N=13\)). A stellar mass dependence is evident, with bulges visible in 80\% of all disk galaxies with mass \(> 10^{9.5}\, {\rm M}_{\odot}\) (\(N=41\)) but only 52\% at \(M < 10^{9.5}\, {\rm M}_{\odot}\) (\(N=82\)). We supplement visual morphologies with non-parametric measurements of Gini and Asymmetry coefficients in the rest-frame $i$-band. Our sources are more asymmetric than local galaxies, with slightly higher Gini values. When compared to high-z rest-frame ultraviolet measurements with Hubble Space Telescope, JWST shows more regular morphological types such as disks, bulges and spiral arms at $z>1.5$, with smoother (i.e. lower Gini) and more symmetrical light distributions.