Clumpiness of galaxies revealed in the near-infrared with COSMOS-Web
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.
Authors
- Nathan Allen (ORCID: https://orcid.org/0000-0001-7876-819X)
- Si-Yue Yu (ORCID: https://orcid.org/0000-0002-3462-4175)
- D. Liu
- Nicolas McMahon
- Marko Shuntov (ORCID: https://orcid.org/0000-0002-7087-0701)
- Boris S. Kalita (ORCID: https://orcid.org/0000-0001-9215-7053)
- H. J. McCracken (ORCID: https://orcid.org/0000-0002-9489-7765)
- G. Aufort
- Caitlin M. Casey (ORCID: https://orcid.org/0000-0002-0930-6466)
- L. Tresse (ORCID: https://orcid.org/0000-0001-8776-0958)
- O. Ilbert (ORCID: https://orcid.org/0000-0002-7303-4397)
- Wilfried Mercier (ORCID: https://orcid.org/0000-0001-6865-499X)
- Maxime Trebitsch (ORCID: https://orcid.org/0000-0002-6849-5375)
- Maximilien Franco (ORCID: https://orcid.org/0000-0002-3560-8599)
- C. Laigle (ORCID: https://orcid.org/0009-0008-5926-818X)
- G. Gozaliasl
- Arianna S. Long (ORCID: https://orcid.org/0000-0002-7530-8857)
- M. Huertas-Company
- Michael Tobias Hirschmann (ORCID: https://orcid.org/0000-0002-4014-424X)
- Rafael C. Arango-Toro (ORCID: https://orcid.org/0000-0002-0569-5222)
- Isabella G. Cox (ORCID: https://orcid.org/0000-0002-1803-794X)
- Jeyhan S. Kartaltepe (ORCID: https://orcid.org/0000-0001-9187-3605)
- Andreas L. Faisst (ORCID: https://orcid.org/0000-0002-9382-9832)
- Y. Dubois
- Hossein Hatamnia (ORCID: https://orcid.org/0009-0007-3673-4523)
- J. Rhodes
- L. Michel-Dansac
Institutions
- University of California, Riverside (US)
- University of Copenhagen (DK)
- American Astronomical Society (US)
- Centre National de la Recherche Scientifique (FR)
- Space Telescope Science Institute (US)
- Jet Propulsion Laboratory (US)
- University of California, Santa Barbara (US)
- Rochester Institute of Technology (US)
- Kavli Institute for the Physics and Mathematics of the Universe (JP)
- University of California, Santa Cruz (US)
- Université Paris Cité (FR)
- Aix-Marseille Université (FR)
- Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR)
- Université Paris Sciences et Lettres (FR)
- Université Paris-Saclay (FR)
- Trieste Astronomical Observatory (IT)
- Institut d'Astrophysique de Paris (FR)
- Purple Mountain Observatory (CN)
- Sorbonne Université (FR)
- Astrophysique, Instrumentation et Modélisation (FR)
- DAWN Center for Independent Living (US)
- Institute of Astronomy (RU)
- CEA Paris-Saclay (FR)
- Astronomy and Space (AU)
- École Polytechnique Fédérale de Lausanne (CH)
- University of Tirana (AL)
- The University of Tokyo (JP)
- The University of Texas at Austin (US)
- IAC (United States) (US)
- Aalto University (FI)
Publication Details
- Journal
- Astronomy and Astrophysics
- Published
- 2025-12-02
- DOI
- https://doi.org/10.1051/0004-6361/202555981
- Primary Topic
- Galaxies: Formation, Evolution, Phenomena
- Type
- article
- Field-Weighted Citation Impact
- 0.00