JWST CEERS probes the role of stellar mass and morphology in obscuring galaxies

In recent years, observations have uncovered a population of massive galaxies that are invisible or very faint in deep optical /near-infrared (near-IR) surveys but brighter at longer wavelengths. However, the nature of these optically dark or faint galaxies (OFGs; one of several names given to these objects) is highly uncertain. In this work, we investigate the drivers of dust attenuation in the JWST era. In particular, we study the role of stellar mass, size, and orientation in obscuring star-forming galaxies (SFGs) at 3 < z < 7:5, focusing on the question of why OFGs and similar galaxies are so faint at optical /near-IR wavelengths. We find that stellar mass is the primary proxy for dust attenuation, among the properties studied. E ffective radius and axis ratio do not show a clear link with dust attenuation, with the e ffect of orientation being close to random. However, there is a subset of highly dust attenuated (AV > 1, typically) SFGs, of which OFGs are a specific case. For this subset, we find that the key distinctive feature is their compact size (for massive systems with log( M-*=M (circle dot)) > 10); OFGs exhibit a 30% smaller e ffective radius than the average SFG at the same stellar mass and redshift. On the contrary, OFGs do not exhibit a preference for low axis ratios (i.e., edge-on disks). The results in this work show that stellar mass is the primary proxy for dust attenuation and compact stellar light profiles behind the thick dust columns obscuring typical massive SFGs.

Automated summary

This study investigates the drivers of dust attenuation in the JWST era and finds that stellar mass is the primary factor. Size and orientation do not show a clear link with dust attenuation. Highly dust attenuated star-forming galaxies are characterized by their compact size.