A systematic search for galaxy proto-cluster cores at z ∼ 2. Issue 3 (19th June 2020)

• Record Type: Journal Article
• Authors: Ando, Makoto; Shimasaku, Kazuhiro; Momose, Rieko
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 496:Issue 3(2020)
• Page Start: 3169
• Page End: 3181
• Publication Date: 2020-06-19
• Subjects: galaxies: clusters: general -- galaxies: formation -- galaxies: high-redshift; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa1757
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: 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 ${\sim}1.5\, \mathrm{deg}^{2}$ of the COSMOS field. Using pairs of massive galaxies [log ( M * /M⊙ ) ≥ 11] as tracers of cores, we find 75 candidate cores, among which 54 per cent are estimated to be real. A clustering analysis finds that these cores have an average DMH mass of $2.6_{-0.8}^{+0.9}\times 10^{13}\, \mathrm{M}_{\odot }$, or $4.0_{-1.5}^{+1.8}\, \times 10^{13} \, \mathrm{M}_{\odot }$ 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⊙ ) ≳ 10.5. The quiescent fraction, $0.17_{-0.04}^{+0.04}$ in the mass range 9.0 ≤ log ( M * /M⊙ ) ≤ 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 z ∼ 2 in proto-cluster cores.