Multi-object spectroscopy of low-redshift EIS clusters IV. Reliability of matched-filter results at z~0.3-0.4

TL;DR

This study confirms the reliability of matched-filter cluster redshift estimates at z~0.3-0.4 by spectroscopically analyzing 747 galaxies in 23 EIS fields, revealing diverse cluster properties and galaxy populations.

Contribution

It provides the first spectroscopic validation of matched-filter cluster redshifts at z~0.3-0.4, expanding the confirmed cluster sample and analyzing galaxy populations within these systems.

Findings

75% of candidate systems are confirmed with spectroscopic redshifts.

Approximately 60% of systems have a significant red sequence.

Clusters exhibit a broad range of velocity dispersions and richness.

Abstract

abridged) In this paper we present new redshifts for 747 galaxies in 23 ESO Imaging Survey (EIS) cluster fields. We use the "gap"-technique to search for significant overdensities in redshift space for identifying groups/clusters of galaxies. In this way we spectroscopically confirm systems in 10 of the 23 cluster candidate fields with a matched-filter estimated redshift z_MF=0.3-0.4 and with spectroscopic redshifts in the range from z=0.158 to z=0.534. We find that the systems identified in the present paper span a broad range of one-dimensional velocity dispersion (175-497 km/s) and richness (12L*<=L<=65L*). Both undersampling and contamination by substructures contribute to the uncertainty of these measurements. From the analysis of the colours of the galaxy populations we find that ~60% of the spectroscopically confirmed systems have a "significant" red sequence with a colour matching passive stellar evolution models. With this paper we complete our spectroscopic survey of the fields of 58 EIS cluster candidates with estimated redshifts z<=0.4. We have measured a total of 1954 galaxy redshifts in the range z=0.0065 to z=0.6706. Of the 58 systems we confirm 42 (~75%) with redshifts between z=0.095 and z=0.534.