New X-ray Clusters in the EMSS II: Optical Properties

Abstract

We present optical images for 9 new clusters of galaxies we have found in a reanalysis of the Einstein IPC images comprising the Extended Medium Sensitivity Survey (EMSS). Based on the presence of a red sequence of galaxies in a color-magnitude (CM) diagram, a redshift is estimated for each cluster. Galaxy overdensities (cluster richnesses) are measured in each field using the B_gc statistic which allows their plausible identification with the X-ray emission. The nature of our X-ray detection algorithm suggests that most of these clusters have low X-ray surface brightness (LSB) compared to the previously known EMSS clusters. We compare the optical and X-ray observations of these clusters with the well-studied Canadian Network for Observational Cosmology (CNOC) subsample of the EMSS, and conclude that the new clusters exhibit a similar range of optical richnesses, X-ray luminosities, and, somewhat surprisingly, galaxy populations as the predominantly rich, relaxed EMSS/CNOC clusters.

Accepted to ApJ, 17 pages, 14 figures, uses emulateapj5.sty

References in corpus (4)

• Distant Cluster Hunting I: A Comparison Between the Optical and X-ray Luminosity Functions from an Optical/X-ray Survey
• Chandra X-Ray Observatory Observation of the High-Redshift Cluster MS 1054-0321
• Cluster Evolution in the ROSAT North Ecliptic Pole Survey
• New X-ray Clusters in the EMSS I: Modifications to the XLF

Cited by in corpus (3)

• The WARPS Survey: VI. Galaxy Cluster and Source Identifications from Phase I
• SPT-GMOS: A Gemini/GMOS-South Spectroscopic Survey of Galaxy Clusters in the SPT-SZ Survey
• New X-ray Clusters in the EMSS I: Modifications to the XLF