Clumpiness of galaxies revealed in the near-infrared with COSMOS-Web: Substructures at 1 < z < 4 and their link to stellar mass and star formation

Mercier, W.; Kalita, B. S.; Shuntov, M.; Arango-Toro, R. C.; Ilbert, O.; Tresse, L.; Dubois, Y.; Laigle, C.; Hatamnia, H.; McMahon, N.; Faisst, A. L.; Cox, I. G.; Trebitsch, M.; Michel-Dansac, L.; Yu, S.-Y.; Hirschmann, M.; Huertas-Company, M.; Long, A. S.; Koekemoer, A. M.; Aufort, G.; Lewis, J. S. W.; Gozaliasl, G.; Rich, R. M.; Rhodes, J.; McCracken, H. J.; Casey, C. M.; Kartaltepe, J. S.; Robertson, B. E.; Franco, M.; Liu, D.; Akins, H. B.; Allen, N.; Toft, S.
Referencia bibliográfica

Astronomy and Astrophysics

Fecha de publicación:
2
2026
Número de autores
33
Número de autores del IAC
1
Número de citas
3
Número de citas referidas
0
Descripción
Context. Clumps in the rest-frame UV emission of galaxies at z ≲ 3 have been observed for decades. Since the launch of the James Webb Space Telescope (JWST), a large population is detected in the rest-frame near-infrared (NIR), raising questions about their formation mechanism. Aims. We investigate the presence and properties of NIR overdensities (hereafter substructures, including clumps) in star-forming and quiescent galaxies at 1 < z < 4 to understand their link to the evolution of their host galaxy. Methods. We identified substructures in JWST/NIRCam F277W and F444W residual images at a rest-frame wavelength of 1 μm. Results. The fraction of galaxies with substructures with M★ > 109 M⊙ has steadily decreased with cosmic time from 40% at z = 4 to 10% at z = 1. NIR clumps, the most common type of small substructure, 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 star formation rate (SFR) of the host galaxies. Its evolution with redshift is due to galaxies moving toward lower SFRs at z ≲ 2 and the buildup of low-mass galaxies in the green valley and red sequence. Based on their spatial distribution in edge-on galaxies, we infer that most substructures are produced in situ via disk fragmentation. Galaxy mergers may still play a role at high stellar masses, especially at a low SFR.