Details

Autor(en) / Beteiligte

• Lotz, Jennifer M
• Papovich, Casey
• Faber, S M
• Ferguson, Henry C
• Grogin, Norman
• Guo, Yicheng
• Kocevski, Dale
• Koekemoer, Anton M
• Lee, Kyoung-Soo
• McIntosh, Daniel

Titel

CAUGHT IN THE ACT: THE ASSEMBLY OF MASSIVE CLUSTER GALAXIES AT z = 1.62

Ist Teil von

• The Astrophysical journal, 2013-08, Vol.773 (2), p.1-10

Ort / Verlag

United States

Erscheinungsjahr

2013

Link zum Volltext

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• 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 sub(star) [> or =, slanted] 3 x 10 super(10) M sub([middot in circle]), 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 super(+13) sub(-14)% of all M sub(star) [> or =, slanted] 3 x 10 super(10) M sub([middot in circle]) cluster candidates are observed in either close pair systems or have double nuclei. In contrast, only 11% + or - 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 sub(primary):M sub(satellite) [> or =, slanted] 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 mu m fluxes. Two of the double-nucleated cluster members have X-ray detected active galactic nuclei with L sub(x) > 10 super(43) erg s super(-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.