Early Results from GLASS-JWST. XVIII. A First Morphological Atlas of the 1 < z < 5 Universe in the Rest-frame Optical

May 2023 • 2023ApJ...948L..13J

Authors • Jacobs, C. • Glazebrook, K. • Calabrò, A. • Treu, T. • Nannayakkara, T. • Jones, T. • Merlin, E. • Abraham, R. • Stevens, A. R. H. • Vulcani, B. • Yang, L. • Bonchi, A. • Boyett, K. • Bradač, M. • Castellano, M. • Fontana, A. • Marchesini, D. • Malkan, M. • Mason, C. • Morishita, T. • Paris, D. • Santini, P. • Trenti, M. • Wang, X.

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 μm NIRCam filters to generate rest-frame gri composite color images, and conduct visual morphological classification. Compared to Hubble Space Telescope (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 ≥ 2 (N = 13). A stellar mass dependence is evident, with bulges visible in 80% of all disk galaxies with mass >10^9.5 M _⊙ (N = 41) but only 52% at M < 10^9.5 M _⊙ (N = 82). We supplement visual morphologies with nonparametric 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 HST, 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.

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Takahiro Morishita

Assistant Scientist