Multi-object spectroscopy of low redshift EIS clusters. III. Properties of optically selected clusters

Abstract

We have carried out an investigation of the properties of low redshift EIS clusters using both spectroscopy and imaging data. We present new redshifts for 738 galaxies in 21 ESO Imaging Survey (EIS) Cluster fields. We use the ``gap''-technique to search for significant overdensities in redshift space and to identify groups/clusters of galaxies corresponding to the original EIS matched filter cluster candidates. In this way we spectroscopically confirm 20 of the 21 cluster candidates with a matched-filter estimated redshift z_MF=0.2. We have now obtained spectroscopic redshifts for 34 EIS cluster candidates with z_MF=0.2 (see also Hansen et al., 2002; Olsen et al., 2003). Of those we spectroscopically confirm 32 with redshifts ranging from z=0.064 to 0.283. We find that: 1) the velocity dispersions of the systems range from sigma_v<=130km/s to sigma_v=1200km/s, typical of galaxy groups to rich clusters; 2) richnesses corresponding to Abell classes R<=1; and 3) concentration indices ranging from C=0.2 to C=1.2. From the analysis of the colours of the galaxy populations we find that 53% of the spectroscopically confirmed systems have a ``significant'' red sequence. These systems are on average richer and have higher velocity dispersions. We find that the colour of the red sequence galaxies matches passive stellar evolution predictions.

24 pages, accepted for publication in A&A

References in corpus (21)

• The Evolution of Early-Type Galaxies in Distant Clusters
• The Observational Distribution of Internal Velocity Dispersions in Nearby Galaxy Clusters
• The Palomar Distant Cluster Survey: I. The Cluster Catalog
• The Cut & Enhance method : selecting clusters of galaxies from the SDSS commissioning data
• The Slope of the Cluster Elliptical Red Sequence: A Probe of Cluster Evolution
• A Merged Catalog of Clusters of Galaxies from Early SDSS Data
• Detecting Clusters of Galaxies in the Sloan Digital Sky Survey I : Monte Carlo Comparison of Cluster Detection Algorithms
• The Color-Magnitude Effect in Early-Type Cluster Galaxies
• The Las Campanas Distant Cluster Survey - The Catalog
• The CNOC2 Field Galaxy Redshift Survey I: The Survey and the Catalog for the Patch CNOC 0223+00
• Evolution in the Color-Magnitude Relation of Early-Type Galaxies in Clusters of Galaxies at z~=1
• The KPNO/Deeprange Distant Cluster Survey: I. The Catalog & the Space Density of Intermediate Redshift Clusters
• Homogeneity of early-type galaxies across clusters
• ESO Imaging Survey VII. Distant Cluster Candidates over 12 square degrees
• Spectroscopic Observations of Optically Selected Clusters of Galaxies from the Palomar Distant Cluster Survey
• Optically-selected clusters at 0.8 < z < 1.3 in the EIS Cluster Survey
• Multi-object spectroscopy of low redshift EIS clusters. I
• Multi-object spectroscopy of low redshift EIS clusters. II
• Comparison of two optical cluster finding algorithms for the new generation of deep galaxy surveys
• On the Nature of the EIS Candidate Clusters: Confirmation of z<0.6 candidates
• CFHT Optical PDCS Survey II: Evolution in the Space Density of Clusters of Galaxies

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• 3D-Matched-Filter Galaxy Cluster Finder I: Selection Functions and CFHTLS Deep Clusters
• NoSOCS in SDSS. I. Sample Definition and Comparison of Mass Estimates
• Empirical Photometric Redshifts of Luminous Red Galaxies and Clusters in SDSS
• Segregation Effects According to the Evolutionary Stage of Galaxy Groups
• New spectroscopic confirmations of high-redshift galaxy clusters
• Multi-object spectroscopy of low-redshift EIS clusters IV. Reliability of matched-filter results at z~0.3-0.4
• Galaxy distribution and evolution around a sample of 2dF groups