2020/02/29 by Makoto Ando, Kazuhiro Shimasaku, Rieko Momose · 1 citation
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.1093/mnras/staa1757
14 pages, 11 figures, accepted for publication in MNRAS, 10th June 2020
arxiv created 2020/06/18 · arxiv updated 2020/06/24
A proto-cluster core is the most massive dark matter halo (DMH) in a given proto-cluster. To reveal the galaxy formation in core regions, we search for proto-cluster cores at z∼ 2 in ∼ 1.5 deg2 of the COSMOS field. Using pairs of massive galaxies (log(M*/M\odot)≥11) as tracers of cores, we find 75 candidate cores, among which 54% are estimated to be real. A clustering analysis finds that these cores have an average DMH mass of 2.6-0.8+0.9× 1013 M\odot, or 4.0-1.5+1.8 × 1013 M\odot after contamination correction. The extended Press-Schechter model shows that their descendant mass at z=0 is consistent with Fornax-like or Virgo-like clusters. Moreover, using the IllustrisTNG simulation, we confirm that pairs of massive galaxies are good tracers of DMHs massive enough to be regarded as proto-cluster cores. We then derive the stellar mass function (SMF) and the quiescent fraction for member galaxies of the 75 candidate cores. We find that the core galaxies have a more top-heavy SMF than field galaxies at the same redshift, showing an excess at log(M*/M\odot)\gtrsim 10.5. The quiescent fraction, 0.17-0.04+0.04 in the mass range 9.0≤ log(M*/M\odot)≤ 11.0, is about three times higher than that of field counterparts, giving an environmental quenching efficiency of 0.13-0.04+0.04. These results suggest that stellar mass assembly and quenching are accelerated as early as at z∼ 2 in proto-cluster cores.