LARgE Survey – I. Dead monsters: the massive end of the passive galaxy stellar mass function at cosmic noon

Abstract

We introduce the largest to date survey of massive quiescent galaxies at redshift &zeta; &sim; 1.6. With these data, which cover 27.6 deg², we can find significant numbers of very rare objects such as ultra-massive quiescent galaxies that populate the extreme massive end of the galaxy mass function, or dense environments that are likely to become present-day massive galaxy clusters. In this paper, the first in a series, we apply our g&zeta;<em>K</em>_s adaptation of the <em>B</em>&zeta;<em>K</em></span>&nbsp;technique to select our &zeta; &sim; 1.6 galaxy catalogue and then study the quiescent galaxy stellar mass function with good statistics over <em>M</em>⋆ &sim; 10^10.2_10^11.7&thinsp;M_⊙ &ndash; a factor of 30 in mass &ndash; including 60 ultra-massive &zeta; &sim; 1.6 quiescent galaxies with <em>M</em>_⋆ &gt; 10^11.5&thinsp;M_⊙. We find that the stellar mass function of quiescent galaxies at &zeta; &sim; 1.6 is well represented by the Schechter function over this large mass range. This suggests that the mass-quenching mechanism observed at lower redshifts must have already been well established by this epoch, and that it is likely due to a single physical mechanism over a wide range of mass. This close adherence to the Schechter shape also suggests that neither merging nor gravitational lensing significantly affects the observed quenched population. Finally, comparing measurements of <strong>M^&lowast; </strong>parameters for quiescent and star-forming populations (ours and from the literature), we find hints of an offset (⁠<strong><em>M</em>^&lowast;_SF&gt;<em>M</em></strong>_{<strong>&lowast;PE</strong>⁠}), which could suggest that the efficiency of the quenching process evolves with time.