Even redder than we knew: Color and A_V evolution up to z = 2.5 from JWST/NIRCam photometry

¹ Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, Belgium
² Physics and Astronomy Department, Tufts University, 574 Boston Avenue, Medford, MA, 02155, USA
³ Department of Physics, University of Bath, Claverton Down, Bath, BA2 7AY, UK
⁴ Department of Astronomy, University of Michigan, 1085 South University Avenue, Ann Arbor, MI, 48109–1107, USA
⁵ Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen, Jagtvej 128, Kóbenhavn N, Copenhagen, DK-2200, Denmark
⁶ Department of Astronomy, University of Massachusetts, Amherst, MA, 01003, USA
⁷ Department of Physics and Astronomy and PITT PACC, University of Pittsburgh, Pittsburgh, PA, 15260, USA
⁸ Department for Astrophysical and Planetary Science, University of Colorado, Boulder, CO, 80309, USA
⁹ University of Kansas, Department of Physics and Astronomy, 1251 Wescoe Hall Drive, Room 1082, Lawrence, KS, 66049, USA
¹⁰ Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 AA Leiden, The Netherlands
¹¹ Department of Astronomy & Astrophysics, The Pennsylvania State University, University Park, PA, 16802, USA
¹² Institute for Computational & Data Sciences, The Pennsylvania State University, University Park, PA, 16802, USA
¹³ Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA, 16802, USA
¹⁴ Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ, UK
¹⁵ Department of Physics, University of California, Santa Barbara, Santa Barbara, CA, 93109, USA
¹⁶ Department of Astronomy, The University of Texas at Austin, Austin, TX, USA
¹⁷ Laboratory for Multiwavelength Astrophysics, School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY, 14623, USA

^⋆ Corresponding author: arjen.vanderwel@ugent.be

Received: 12 May 2025
Accepted: 30 June 2025

Abstract

Aims. JWST/NIRCam provides rest-frame near-IR photometry of galaxies up to z = 2.5 with exquisite depth and accuracy. This affords us an unprecedented view of the evolution of the UV/optical/near-IR color distribution and its interpretation in terms of the evolving dust attenuation, A_V.

Methods. We used the value-added data products (photometric redshift, stellar mass, rest-frame U − V and V − J colors, and A_V) provided by the public DAWN JWST Archive. These data products derive from fitting the spectral energy distributions obtained from multiple NIRCam imaging surveys, augmented with preexisting HST imaging data. Our sample consists of a stellar-mass-complete sample of ≈28 000M_⋆ >  10⁹ M_⊙ galaxies in the redshift range 0.5 <  z <  2.5.

Results. The V − J color distribution of star-forming galaxies evolves strongly, in particular for high-mass galaxies (M_⋆ >  3 × 10¹⁰ M_⊙), which have a pronounced tail of very red galaxies reaching V − J >  2.5 at z >  1.5 that does not exist at z <  1. Such red V − J can only be explained by dust attenuation, with typical values for M_⋆ ≈ 10¹¹ M_⊙ galaxies in the range A_V ≈ 1.5 − 3.5 at z ≈ 2. This redshift evolution went largely unnoticed before. Today, however, photometric redshift estimates for the reddest (V − J >  2.5), most attenuated galaxies have markedly improved thanks to the new, precise photometry, which is in much better agreement with the 25 available spectroscopic redshifts for such galaxies. The reddest population readily stands out as the independently identified population of galaxies detected at submillimeter wavelengths. Despite the increased attenuation, U − V colors across the entire mass range are slightly bluer at higher z. A well-defined and tight color sequence exists at redshifts 0.5 <  z <  2.5 for M_⋆ >  3 × 10¹⁰ M_⊙ quiescent galaxies, in both U − V and V − J, but in V − J it is bluer rather than redder compared to star-forming galaxies. In conclusion, whereas the rest-frame UV-optical color distribution evolves remarkably little from z = 0.5 to z = 2.5, the rest-frame optical/near-IR color distribution evolves strongly, primarily due to a very substantial increase with redshift in dust attenuation for massive galaxies.