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

Massive, high-redshift ( z &gt; 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 ∗ &gt; 10 9.5 M ⊙ ) quiescent galaxies from z = 2 − 7 in over 800 arcmin 2 of NIRCam imaging from a compilation of public JWST fields (with a total area &gt; 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 ∗ &lt; 10 10 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.