An X-Ray{endash}Selected Galaxy Cluster at {bold {ital z}} = 1.26
- Physics Department, University of California at Davis, Davis, CA 95616 (United States)
- Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, P.O. Box 808, L-413, Livermore, CA 94550 (United States)
- Department of Astronomy, 601 Campbell Hall No. 3411, University of California, Berkeley, CA 94720 (United States)
- National Optical Astronomy Observatories, 950 North Cherry Avenue, Tucson, AZ 85726-6732 (United States)
We report the discovery of an X-ray{endash}luminous galaxy cluster at z=1.26. RX J0848.9+4452 was selected as an X-ray cluster candidate in the {ital ROSAT} Deep Cluster Survey on the basis of its spatial extent. Deep optical and near-IR imaging have revealed a galaxy overdensity around the peak of the X-ray emission, with a significant excess of red objects with {ital J}{minus}{ital K} colors typical of elliptical galaxies at z{gt}1. Spectroscopic observations at the Keck II Telescope have secured six galaxy redshifts in the range 1.257{lt}z{lt}1.267 ({l_angle}z{r_angle}=1.261) within a 35{double_prime} radius around the peak X{endash}ray emission. This system lies only 4&arcmin;2 away (5.0thinsph{sup {minus}1} {sub 50} comoving Mpc, q{sub 0} =0.5) from the galaxy cluster ClG J0848+4453, which was identified at z=1.273 in a near-IR field galaxy survey and is also known to be X-ray luminous. Assuming that the X-ray emission is entirely due to hot intracluster gas, both these systems have similar rest-frame luminosities L{sub X} {approx}1{times}10{sup 44} ergs s{sup {minus}1} (0.5{endash}2.0 keV band). In combination with our spectrophotometric data for the entire 30 arcmin{sup 2} field, this suggests the presence of a superstructure consisting of two collapsed, possibly virialized, clusters, the first detected to date at z{gt}1. {copyright} {ital {copyright} 1999.} {ital The American Astronomical Society}
- OSTI ID:
- 698820
- Journal Information:
- Astronomical Journal, Journal Name: Astronomical Journal Journal Issue: 1 Vol. 118; ISSN 0004-6256; ISSN ANJOAA
- Country of Publication:
- United States
- Language:
- English
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