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Title: EVIDENCE FOR A GAS-RICH MAJOR MERGER IN A PROTO-CLUSTER AT z = 2.5

Gas-rich major mergers in high-redshift proto-clusters are important events, perhaps leading to the creation of the slowly rotating remnants seen in the cores of clusters in the present day. Here, we present a deep Jansky Very Large Array observation of CO J = 1-0 emission line in a proto-cluster at z = 2.5, USS1558-003. The target field is an extremely dense region, where 20 Hα emitters (HAEs) are clustering. We have successfully detected the CO emission line from three HAEs and discovered a close pair of red and blue CO-emitting HAEs. Given their close proximity (∼30 kpc), small velocity offset (∼300 km s{sup –1}), and similar stellar masses, they could be in the early phase of a gas-rich major merger. For the red HAE, we derive a total infrared luminosity of L {sub IR} = 5.1 × 10{sup 12} L {sub ☉} using MIPS 24 μm and radio continuum images. The L{sub IR}/L{sub CO}{sup ′} ratio is significantly enhanced compared to local spirals and high-redshift disks with a similar CO luminosity, which is indicative of a starburst mode. We find the gas depletion timescale is shorter than that of normal star-forming galaxies regardless of adopted CO-H{sub 2} conversion factors. The identification of suchmore » a rare event suggests that gas-rich major mergers frequently take place in proto-clusters at z > 2 and may involve the formation processes of slow rotators seen in local massive clusters.« less
Authors:
; ; ; ;  [1] ; ; ;  [2] ;  [3] ;  [4]
  1. National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)
  2. Institute of Astronomy, The University of Tokyo, Mitaka, Tokyo 181-0015 (Japan)
  3. Department of Astronomical Science, The Graduate University for Advanced Studies, Mitaka, Tokyo 181-8588 (Japan)
  4. Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, HI 96720 (United States)
Publication Date:
OSTI Identifier:
22365784
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 788; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON MONOXIDE; COMPARATIVE EVALUATIONS; CONVERSION; GALAXIES; HYDROGEN; LUMINOSITY; MASS; RED SHIFT; STAR CLUSTERS; STAR EVOLUTION; STARS; VELOCITY