1999AJ....118...76R -
Astron. J., 118, 76-85 (1999/July-0)
An X-Ray-selected galaxy cluster at z = 1.26.
ROSATI P., STANFORD S.A., EISENHARDT P.R., ELSTON R., SPINRAD H., STERN D. and DEY A.
Abstract (from CDS):
We report the discovery of an X-ray-luminous galaxy cluster at z=1.26. RX J0848.9+4452 was selected as an X-ray cluster candidate in the 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 J-K colors typical of elliptical galaxies at z>1. Spectroscopic observations at the Keck II Telescope have secured six galaxy redshifts in the range 1.257<z<1.267 (<z≥1.261) within a 35" radius around the peak X-ray emission. This system lies only 4'.2 away (5.0 h–150 comoving Mpc, q0=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 LX~1x1044 ergs.s–1 (0.5-2.0 keV band). In combination with our spectrophotometric data for the entire 30 arcmin2 field, this suggests the presence of a superstructure consisting of two collapsed, possibly virialized, clusters, the first detected to date at z>1.
Abstract Copyright:
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Journal keyword(s):
Galaxies: Clusters: General - Galaxies: Evolution - Galaxies: Formation - X-Rays
Nomenclature:
Table 2: [RSE99] NNN N=10 among (Nos 1-248).
Simbad objects:
16
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