Assembly of massive galaxies in a high-z protocluster

Yuka K. Uchimoto, Toru Yamada, Masaru Kajisawa, Mariko Kubo, Takashi Ichikawa, Yuichi Matsuda, Masayuki Akiyama, Tomoki Hayashino, Masahiro Konishi, Tetsuo Nishimura, Koji Omata, Ryuji Suzuki, Ichi Tanaka, Chihiro Tokoku, Tomohiro Yoshikawa

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)


We present the results of wide-field deep JHK imaging of the SSA22 field using the MOIRCS instrument equipped with the Subaru telescope. The observed field is 112 arcmin2 in area, which covers the z = 3.1 protocluster characterized by the overdensities of Lyα emitters (LAEs) and Lyα blobs (LABs). The 5σ limiting magnitude is K AB = 24.3. We extract the potential protocluster members from the K-selected sample by using the multi-band photometric-redshift selection as well as the simple color cut for distant red galaxies (DRGs; J - K AB > 1.4). The surface number density of DRGs in our observed fields shows clear excess compared with those in the blank fields, and the location of the densest area whose projected overdensity is twice the average coincides with the large-scale density peak of LAEs. We also found that K-band counterparts with z phot ≃ 3.1 are detected for 75% (15/20) of the LABs within their Lyα halo, and the 40% (8/20) of LABs have multiple components, which gives a direct evidence of the hierarchical multiple merging in galaxy formation. The stellar mass of LABs correlates with their luminosity, isophotal area, and the Lyα velocity widths, implying that the physical scale and the dynamical motion of Lyα emission are closely related to their previous star formation activities. Highly dust-obscured galaxies such as hyper extremely red objects (J - K AB > 2.1) and plausible K-band counterparts of submillimeter sources are also populated in the high-density region.

Original languageEnglish
Article number116
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 2012 May 10


  • cosmology: observations
  • galaxies: clusters: general
  • galaxies: evolution
  • galaxies: formation
  • galaxies: high-redshift

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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