Clumpiness of galaxies revealed in the near-infrared with COSMOS-Web
Year: 2025
Type: article
Abstract: 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 ★ > 10 9 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.
Source: Astronomy and Astrophysics
Authors: W. Mercier, B. S. Kalita, M. Shuntov, R. C. Arango-Toro, O. Ilbert, L. Tresse, Y. Dubois, C. Laigle, H. Hatamnia, N. McMahon, A. L. Faisst, I. G. Cox, M. Trebitsch, L. Michel-Dansac, S.-Y. Yu, M. Hirschmann, A. S. Long, A. M. Koekemoer, G. Aufort, J. S. W. Lewis, G. Gozaliasl, R. M. Rich, J. Rhodes, H. J. McCracken, C. M. Casey, J. S. Kartaltepe, B. E. Robertson, M. Franco, D. Liu, H. B. Akins, N. Allen, S. Toft
Institutions: Centre National de la Recherche Scientifique, Aix-Marseille Université, Kavli Institute for the Physics and Mathematics of the Universe, Peking University, The University of Tokyo, University of Copenhagen, Institut d'Astrophysique de Paris, Université Pierre-et-Marie-Curie, University of California, Riverside, Rochester Institute of Technology, California Institute of Technology, Infrared Processing and Analysis Center, Université Paris Sciences et Lettres, Observatoire de Paris, Sorbonne Université, Trieste Astronomical Observatory, École Polytechnique Fédérale de Lausanne, National Institute for Astrophysics, University of Washington, Space Telescope Science Institute, Aalto University, University of California, Los Angeles, Jet Propulsion Laboratory, University of California, Santa Barbara, The University of Texas at Austin, University of California, Santa Cruz, Université Paris Cité, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Université Paris-Saclay, Astrophysique, Instrumentation et Modélisation, Chinese Academy of Sciences, Purple Mountain Observatory
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W4416926518