Rest-frame NIR substructures detections

We identify substructures in JWST/NIRCam F277W and F444W residual images at a rest-frame wavelength of 1um. The fraction of galaxies with substructures with M*>10^9^M_{sun}_ has steadily decreased with cosmic time from 40% at z=4 to 10% at z=1. NIR clumps, the most common type of small substructures, are much fainter (2% of the total galaxy flux) than similar UV clumps in the literature.

Nearly all galaxies at the high-mass end of the main sequence (MS), starburst, and green valley regions have substructures. However, we do not find substructures in low-mass galaxies in the green valley and red sequence. Although massive galaxies on the MS and in the green valley have a 40% probability of hosting multiple clumps, the majority of clumpy galaxies host only a single clump.

Conclusions: The fraction of clumpy galaxies in the rest-frame NIR is determined by the stellar mass and SFR of the host galaxies. Its evolution with redshift is due to galaxies moving toward lower SFRs at z<2 and the build-up of low-mass galaxies in the green valley and red sequence. Based on their spatial distribution in edge-on galaxies, we infer that most of substructures are produced in-situ via disk fragmentation.

Galaxy mergers may still play a role at high stellar masses, especially at low SFR.