TY - JOUR
T1 - The formation of the massive galaxies in the SSA22 z = 3.1 protocluster
AU - Kubo, M.
AU - Uchimoto, Y. K.
AU - Yamada, T.
AU - Kajisawa, M.
AU - Ichikawa, T.
AU - Matsuda, Y.
AU - Akiyama, M.
AU - Hayashino, T.
AU - Konishi, M.
AU - Nishimura, T.
AU - Omata, K.
AU - Suzuki, R.
AU - Tanaka, I.
AU - Yoshikawa, T.
AU - Alexander, D. M.
AU - Fazio, G. G.
AU - Huang, J. S.
AU - Lehmer, B. D.
PY - 2013/12/1
Y1 - 2013/12/1
N2 - We study the properties of K-band-selected galaxies (K AB < 24) in the z = 3.09 SSA22 protocluster field. 430 galaxies at 2.6 < z phot < 3.6 are selected as potential protocluster members in a 112 arcmin2 area based on their photometric redshifts. We find that ≈20% of the massive galaxies with stellar masses >1011 M ⊙ at z 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 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. A 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.
AB - We study the properties of K-band-selected galaxies (K AB < 24) in the z = 3.09 SSA22 protocluster field. 430 galaxies at 2.6 < z phot < 3.6 are selected as potential protocluster members in a 112 arcmin2 area based on their photometric redshifts. We find that ≈20% of the massive galaxies with stellar masses >1011 M ⊙ at z 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 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. A 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.
KW - cosmology: observations
KW - galaxies: clusters: general
KW - galaxies: evolution
KW - galaxies: formation
KW - galaxies: high-redshift
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U2 - 10.1088/0004-637X/778/2/170
DO - 10.1088/0004-637X/778/2/170
M3 - Article
AN - SCOPUS:84887927521
VL - 778
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2
M1 - 170
ER -