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Title: The formation of the massive galaxies in the SSA22 z = 3.1 protocluster

We study the properties of K-band-selected galaxies (K {sub AB} < 24) in the z = 3.09 SSA22 protocluster field. 430 galaxies at 2.6 < z {sub phot} < 3.6 are selected as potential protocluster members in a 112 arcmin{sup 2} area based on their photometric redshifts. We find that ≈20% of the massive galaxies with stellar masses >10{sup 11} M {sub ☉} at z {sub phot} ∼ 3.1 have colors consistent with those of quiescent galaxies with ages >0.5 Gyr. This fraction increases to ≈50% after correcting for unrelated foreground/background objects. We also find that 30% of the massive galaxies are heavily reddened, dusty, star-forming galaxies. Few such quiescent galaxies at similar redshifts are seen in typical survey fields. An excess surface density of 24 μm sources at z {sub phot} ∼ 3.1 is also observed, implying the presence of dusty star-formation activity in the protocluster. Cross-correlation with the X-ray data indicates that the fraction of K-band-selected protocluster galaxies hosting active galactic nuclei (AGNs) is also high compared with the field. The sky distribution of the quiescent galaxies, the 24 μm sources, and the X-ray AGNs show clustering around a density peak of z = 3.1 Lyα emitters. Amore » significant fraction of the massive galaxies have already become quiescent, while dusty star-formation is still active in the SSA22 protocluster. These findings indicate that we are witnessing the formation epoch of massive early-type galaxies in the centers of the predecessors to present-day rich galaxy clusters.« less
Authors:
; ; ; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ; ; ; ;  [6] ;  [7] ;  [8] ; ;  [9] ;  [10]
  1. Astronomical Institute, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi, 980-8578 (Japan)
  2. Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577 (Japan)
  3. Chile Observatory, National Astronomical Observatory of Japan, Tokyo 181-8588 (Japan)
  4. Research Center for Neutrino Science, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai, Miyagi, 980-8578 (Japan)
  5. Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo, 181-0015 (Japan)
  6. Subaru Telescope, National Astronomical Observatory of Japan, 650 North Aohoku Place, Hilo, HI 96720 (United States)
  7. Koyama Astronomical Observatory, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555 (Japan)
  8. Department of Physics, Durham University, Durham DH1 3LE (United Kingdom)
  9. Center for Astrophysics, Cambridge, MA 02138 (United States)
  10. The Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States)
Publication Date:
OSTI Identifier:
22341900
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 778; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COLOR; COMPARATIVE EVALUATIONS; CORRELATIONS; COSMOLOGY; DENSITY; DISTRIBUTION; EVOLUTION; GALAXIES; GALAXY CLUSTERS; GALAXY NUCLEI; MASS; RED SHIFT; SKY; STARS; SURFACES; X RADIATION