RX J0848+4456: Disentangling a Moderate Redshift Cluster
Abstract
We present a multiwavelength study of RX J0848+4456, a cluster of galaxies discovered through X-ray emission in the ROSAT Deep Cluster Survey. Our observations consist of WFPC2 imaging, optical spectra, and X-ray data collected with the Chandra X-Ray Observatory. We find that RX J0848+4456 consists of an X-ray-emitting cluster of galaxies at a redshift of z=0.570 and a group at a slightly lower redshift, z=0.543, with little X-ray emission. This lower redshift system, however, is a gravitational lens, with the lensed galaxy being an unusual AGN or star-forming system at z=3.356. The cluster has an X-ray temperature of kT=3.6+/-0.4 keV, a bolometric luminosity of 1.0+/-0.3×1044 ergs s-1 and a velocity dispersion of 670+/-50 km s-1. These values all agree with the low-redshift correlations for clusters of galaxies, implying a relaxed system with the intracluster medium in equilibrium with the dark matter potential. The lower redshift group of galaxies at z=0.543 has, at most, one-fifth, and more likely 1/10, of the X-ray luminosity of RX J0848+4456. Despite being a gravitational lens, this is a low-mass system, with an X-ray temperature of kT=2.3+0.5-0.4 keV and a velocity dispersion of only 430+/-20 km s-1. Our observations show the importance of detailed studies of clusters of galaxies when using them as probes of cosmological mass functions. Based on observations with the NASA/ESA Hubble Space Telescope (HST), obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5-26555.
- Publication:
-
The Astronomical Journal
- Pub Date:
- August 2001
- DOI:
- 10.1086/321163
- arXiv:
- arXiv:astro-ph/0105011
- Bibcode:
- 2001AJ....122..629H
- Keywords:
-
- Catalogs;
- Cosmology: Observations;
- Galaxies: Clusters: General;
- Astrophysics
- E-Print:
- 19 pages, AAS LaTeX, 6 figures including two in color. Accepted for publication in the August 2001 Astronomical Journal Minor modifications to match published version