The stellar mass function of quiescent and star-forming galaxies and its dependence on morphology in COSMOS-Web

¹ Cosmic Dawn Center (DAWN), Denmark
² Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen, Denmark
³ Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
⁴ Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
⁵ International Centre for Radio Astronomy Research (ICRAR), M468, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
⁶ The University of Texas at Austin, 2515 Speedway Blvd Stop C1400, Austin, TX 78712, USA
⁷ Department of Astronomy, University of Washington Seattle, WA 98105, USA
⁸ Instituto de Física y Astronomía, Universidad de Valparaíso, Avda. Gran Bretana 1111 Valparaíso, Chile
⁹ Millennium Nucleus for Galaxies (MINGAL), Santiago, Chile
¹⁰ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
¹¹ Department of Computer Science, Aalto University, P.O. Box 15400, FI-00076, Espoo, Finland
¹² Department of Physics, University of, P.O. Box 64, FI-00014 Helsinki, Finland
¹³ Department of Physics and Astronomy, University of California, Riverside, 900 University Ave, Riverside, CA 92521, USA
¹⁴ Laboratory for Multiwavelength Astrophysics, School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623, USA
¹⁵ Institut de Physique, GalSpec, École Polytechnique Fédérale de Lausanne, Observatoire de Sauverny, Chemin Pegasi 51, 1290 Versoix, Switzerland
¹⁶ Istituto Nazionale di Astrofisica (INAF), Astronomical Observatory of Trieste, Via Tiepolo 11, 34131 Trieste, Italy
¹⁷ Instituto de Astrofísica de Canarias (IAC), La Laguna E-38205, Spain
¹⁸ Observatoire de Paris, LERMA, PSL University, 61 avenue de l’Observatoire, F-75014 Paris, France
¹⁹ Université Paris-Cité, 5 Rue Thomas Mann, 75014 Paris, France
²⁰ Universidad de La Laguna, Avda. Astrofísico Fco. Sanchez, La Laguna, Tenerife, Spain
²¹ DTU Space, Technical University of Denmark, Elektrovej, Building 328, 2800 Kgs. Lyngby, Denmark
²² Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
²³ Institut d’Astrophysique de Paris, UMR 7095, CNRS, Sorbonne Université, 98 bis boulevard Arago, F-75014 Paris, France
²⁴ European Space Agency (ESA), European Space Astronomy Centre (ESAC), Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
²⁵ Istituto Nazionale di Astrofisica (INAF), Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
²⁶ Department of Physics and Astronomy, UCLA, PAB 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547, USA
²⁷ Institute for Astronomy, University of Hawai’i at Manoa, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
²⁸ University of Bologna – Department of Physics and Astronomy “Augusto Righi” (DIFA), Via Gobetti 93/2, I-40129 Bologna, Italy
²⁹ INAF–Osservatorio di Astrofisica e Scienza dello Spazio, Via Gobetti 93/3, I-40129 Bologna, Italy
³⁰ Zentrum für Astronomie, Universität Heidelberg, Philosophenweg 12, D-69120 Heidelberg, Germany
³¹ Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA

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Received: 7 November 2025
Accepted: 4 February 2026

Abstract

We study the stellar mass function (SMF) of quiescent and star-forming galaxies and its dependence on morphology in ten redshift bins at 0.2 < z < 5.5. We used the COSMOS2025 catalog, built from the 0.54 deg² JWST imaging from the COSMOS-Web survey, to select galaxies by type using the NUVrJ rest-frame color diagram and to classify them morphologically based on their bulge-to-total light ratio (B/T). The SMF of quiescent galaxies shows a rapid early build-up, with the most massive, log(M_★/M_⊙)≳11, being assembled by z ∼ 1 and evolving little since. The star-forming SMF evolves more slowly with redshift, following a mass-evolution scenario where galaxies grow in mass via star formation and quench once they reach the characteristic log(M^∗/M_⊙) ∼ 10.6. Bulge systems (B/T > 0.6) dominate the quiescent SMF at log(M_★/M_⊙) > 10 at all redshifts, while disk systems (B/T < 0.2) dominate at log(M_★/M_⊙) < 9. However, most bulge-dominated galaxies in the Universe are star forming, with their fraction increasing with redshift and decreasing mass, consistent with them being progenitors of quiescent bulges. We find evidence for the onset of environmental quenching as early as z ∼ 3 from the upturn in the quiescent SMF at log(M_★/M_⊙) < 9.5. This upturn is contributed by disk-dominated galaxies, consistent with environmental quenching scenarios in which satellites are quenched, but retain their disk morphologies. The number densities of log(M_★/M_⊙) > 10 quiescent galaxies are lower than in the recent literature by 0.1 − 0.7 dex, but agree well with cosmological galaxy formation simulations at 2 < z < 3. However, at z > 3, simulations increasingly underpredict the observations. Finally, we built a simple empirical model to describe the redshift evolution of galaxy number densities by parameterizing the quenching rate of all and bulge-dominated galaxies, stellar fraction, and bulge formation function. Our model is consistent with an evolutionary scenario where star-forming galaxies grow a central bulge before permanently quenching in massive halos.