The Formation of the Massive Galaxies in the SSA22 z = 3.1 Protocluster

Kubo, M.; Uchimoto, Y.K.; Yamada, T.; Kajisawa, M.; Ichikawa, T.; Matsuda, Y.; Akiyama, M.; Hayashino, T.; Konishi, M.; Nishimura, T.; Omata, K.; Suzuki, R.; Tanaka, I.; Yoshikawa, T.; Alexander, D.M.; Fazio, G.G.; Huang, J.-S.; Lehmer, B.D.

Abstract

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.

Citation

Kubo, M., Uchimoto, Y., Yamada, T., Kajisawa, M., Ichikawa, T., Matsuda, Y., …Lehmer, B. (2013). The Formation of the Massive Galaxies in the SSA22 z = 3.1 Protocluster. Astrophysical Journal, 778(2), Article 170. https://doi.org/10.1088/0004-637x/778/2/170

• Journal Article Type: Article
• Publication Date: Dec 1, 2013
• Deposit Date: Nov 22, 2013
• Publicly Available Date: Jun 27, 2014
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 778
• Issue: 2
• Article Number: 170
• DOI: https://doi.org/10.1088/0004-637x/778/2/170
• Keywords: Cosmology: observations, Galaxies: clusters: general, Galaxies: evolution, Galaxies: formation, Galaxies: high-redshift.
• Public URL: https://durham-repository.worktribe.com/output/1446802