Discovery of a High-Redshift ([CLC][ITAL]z[/ITAL][/CLC] = 0.96) Cluster of Galaxies Using a FIRST Survey Wide-Angle–Tailed Radio Source

Abstract

Using a combination of near-infrared and optical photometry, along with multiobject spectroscopy, we have confirmed the existence of a high-redshift cluster of galaxies at z = 0.96. The cluster was found using a wide-angle–tailed radio source selected from the VLA FIRST survey as a cluster signpost. These types of radio sources are often found in clusters and are thought to attain their C-shaped morphologies from the relative motion between the radio source host galaxy and the intracluster medium.We present optical/near- infrared color-magnitude diagrams that show a concentration of cluster galaxies in color space. We also include spectroscopic results obtained from the Keck II Low Resolution Imaging Spectrometer. Ten galaxies are confirmed at the cluster redshift, with a line-of-sight velocity dispersion of ?k ¼ 530þ190 ?90 km s?1, typical of an Abell richness class 0 cluster. Using data from the ROSAT public archive, we limit the X-ray luminosity for the cluster to LX,bold3 ? 1044 ergs s?1, consistent with the value expected from the LX-? relation