Exploring over 700 massive quiescent galaxies at z = 2–7: Demographics and stellar mass functions

¹ DARK, Niels Bohr Institute, University of Copenhagen, Jagtvej 155A, DK-2200 Copenhagen, Denmark
² Cosmic Dawn Center (DAWN), Copenhagen, Denmark
³ DTU Space, Technical University of Denmark, Elektrovej 327, DK- 2800 Kgs. Lyngby, Denmark
⁴ International Centre for Radio Astronomy Research (ICRAR), M468,University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
⁵ ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia
⁶ Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA
⁷ Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen N, Denmark

^⋆ Corresponding author: william.baker@nbi.ku.dk

Received: 5 June 2025
Accepted: 10 September 2025

Abstract

Massive, high-redshift (z >  2) quiescent galaxies represent crucial tests of early galaxy formation and evolutionary mechanisms through their cosmic number densities and stellar mass functions (SMFs). We explore a sample of 743 massive (M_∗ > 10^9.5 M_⊙) quiescent galaxies from z = 2 − 7 in over 800 arcmin² of NIRCam imaging from a compilation of public JWST fields (with a total area > 5× previous JWST studies). We compute and report their cosmic number densities, stellar mass functions, and cosmic stellar mass density. We confirm a significant overabundance of massive quiescent galaxies relative to a range of cosmological hydrodynamical simulations and semi-analytic models (SAMs). We find that no simulations or SAMs accurately reproduce the SMF for massive quiescent galaxies at any redshift within the interval z = 2 − 5. This shows that none of these models’ feedback prescriptions are fully capturing high-z galaxy quenching, challenging the standard formation scenarios. We find a greater abundance of lower-mass (M_∗ < 10¹⁰ M_⊙) quiescent galaxies than has been previously found, highlighting the importance of specific-star-formation rate cuts rather than simple colour selection. We show the importance of this selection bias, alongside individual field-to-field variations caused by cosmic variance, in varying the observed quiescent galaxy SMF, especially at higher z. We also find a steeper increase in the cosmic stellar mass density for massive quiescent galaxies than has been seen previously, with ρ_* ∝ (1 + z)^{−7.2 ± 0.3}, indicating the dramatic increase in the importance of galaxy quenching within these epochs.