COSMOS-Web: The emergence of the Hubble sequence

¹ Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain
² Universidad de la Laguna, La Laguna, Tenerife, Spain
³ Université de Paris, LERMA – Observatoire de Paris, PSL, Paris, France
⁴ Cosmic Dawn Center (DAWN), Denmark
⁵ Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen, Denmark
⁶ ETH, Switzerland
⁷ Dunlap Institute for Astronomy & Astrophysics, University of Toronto, Toronto, Canada
⁸ Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
⁹ Institut d’Astrophysique de Paris, UMR 7095, CNRS, Sorbonne Université, 98 bis boulevard Arago, F-75014 Paris, France
¹⁰ The University of Texas at Austin, 2515 Speedway Blvd Stop C1400, Austin, TX 78712, USA
¹¹ Centro de Astrobiología (CAB), CSIC-INTA, Ctra. de Ajalvir km 4, Torrejón de Ardoz, E-28850 Madrid, Spain
¹² Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel
¹³ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
¹⁴ Physics Department, Lancaster University, Lancaster LA1 4YB, UK
¹⁵ Laboratory for Multiwavelength Astrophysics, School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623, USA
¹⁶ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁷ Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
¹⁸ Purple Mountain Observatory, Chinese Academy of Sciences, 10 Yuanhua Road, Nanjing 210023, China
¹⁹ Center for Astrophysics | Harvard & Smithsonian, 60 Garden St, Cambridge, MA 02138, USA
²⁰ Black Hole Initiative, Harvard University, 20 Garden St, Cambridge, MA 02138, USA
²¹ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109
²² Department of Astronomy and Astrophysics, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
²³ Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo, Kashiwa, Chiba 277-8583, Japan
²⁴ Institute for Physics, Laboratory for Galaxy Evolution and Spectral modelling, Ecole Polytechnique Federale de Lausanne, Observatoire de Sauverny, Chemin Pegasi 51, 1290 Versoix, Switzerland
²⁵ Departments of Astronomy and Physics, Haverford College, 370 Lancaster Ave., Haverford, PA 19041, USA
²⁶ Department of Phyiscs University of California Santa Barbara, CA 93106, CA
²⁷ Department of Computer Science, Aalto University, PO Box 15400 Espoo FI-00 076, Finland
²⁸ Department of Physics, Faculty of Science, University of Helsinki, 00014 Helsinki, Finland
²⁹ Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Kotlářská 2, Brno 611 37, Czech Republic

^⋆ Corresponding author: mhuertas@iac.es

Received: 16 January 2025
Accepted: 1 July 2025

Abstract

Context. The first JWST deep surveys have expanded our understanding of the morphological evolution of galaxies across cosmic time. The improved spatial resolution and near-infrared (NIR) coverage have revealed a population of morphologically evolved galaxies at very early epochs. However, all previous works are based on relatively small samples; this has prevented accurate probing of the morphological diversity at cosmic dawn.

Aims. Leveraging the wide area coverage of the COSMOS-Web survey, we quantified the abundance of different morphological types from z ∼ 7 with unprecedented statistics and established robust constraints on the epoch of emergence of the Hubble sequence.

Methods. We measured the global morphologies (spheroids, disk-dominated, bulge-dominated, peculiar) and resolved morphologies (stellar bars) for about 400 000 galaxies down to F150W = 27 using deep learning; this represents an increase of two orders of magnitude over previous studies. We provide reference stellar mass functions (SMFs) of different morphologies between z ∼ 0.2 and z ∼ 7 as well as best-fit parameters to inform models of galaxy formation. All catalogs and data are made publicly available.

Results. At redshift z > 4.5, the massive galaxy population (log M_*/M_⊙ > 10) is dominated by disturbed morphologies (∼ 70%), even in the optical rest frame, and very compact objects (∼ 30%) with effective radii smaller than ∼ 500 pc. This confirms that a significant fraction of the star formation at cosmic dawn occurs in very dense regions, although the stellar mass for these systems could be overestimated. Galaxies with Hubble-type morphologies, including bulge- and disk-dominated galaxies, arose rapidly around z ∼ 4 and dominate the morphological diversity of massive galaxies as early as z ∼ 3. Using stellar bars as a proxy, we speculate that stellar disks in massive galaxies might have been common (> 50%) among the star-forming population since cosmic noon (z ∼ 2--2.5) and formed as early as z ∼ 7. Massive quenched galaxies are predominantly bulge-dominated from z ∼ 4 onward, suggesting that morphological transformations briefly precede or are simultaneous to quenching mechanisms at the high-mass end. Low-mass (log M_*/M_⊙ < 10) quenched galaxies are typically disk-dominated, which points to different quenching routes at the two ends of the stellar mass spectrum from cosmic dawn.