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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 693599.0, MPI für Astronomie / Publikationen_mpia
Caught in the Act: the assembly of massive cluster galaxies at z = 1.62
Authors:Lotz, J. M.; Papovich, C.; Faber, S. M.; Ferguson, H. C.; Grogin, N.; Guo, Y.; Kocevski, D.; Koekemoer, A. M.; Lee, K.-S.; McIntosh, D.; Momcheva, I.; Rudnick, G.; Saintonge, A.; Tran, K.-V.; van der Wel, A.; Willmer, C.
Date of Publication (YYYY-MM-DD):2013
Title of Journal:The Astrophysical Journal
Start Page:id. 154 (10 pp)
Audience:Not Specified
Abstract / Description:We present the recent merger history of massive galaxies in a spectroscopically confirmed proto-cluster at z = 1.62. Using Hubble Space Telescope WFC3 near-infrared imaging from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we select cluster and z ~ 1.6 field galaxies with M star >= 3 × 1010 M , to determine the frequency of double nuclei or close companions within projected separations less than 20 kpc co-moving. We find that four out of five spectroscopically confirmed massive proto-cluster galaxies have double nuclei, and 57 ^{+13}_{-14}% of all M star >= 3 × 1010 M cluster candidates are observed in either close pair systems or have double nuclei. In contrast, only 11% ± 3% of the field galaxies are observed in close pair/double nuclei systems. After correcting for the contribution from random projections, the implied merger rate per massive galaxy in the proto-cluster is ~3-10 times higher than the merger rate of massive field galaxies at z ~ 1.6. Close pairs in the cluster have minor merger stellar mass ratios (M primary: M satellite >= 4), while the field pairs consist of both major and minor mergers. At least half of the cluster mergers are gas-poor, as indicated by their red colors and low 24 μm fluxes. Two of the double-nucleated cluster members have X-ray detected active galactic nuclei with Lx > 1043 erg s-1, and are strong candidates for dual or offset super-massive black holes. We conclude that the massive z = 1.62 proto-cluster galaxies are undergoing accelerated assembly via minor mergers, and discuss the implications for galaxy evolution in proto-cluster environments.
Free Keywords:galaxies: clusters: general; galaxies: high-redshift; galaxies: interactions
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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