Issue |
A&A
Volume 435, Number 3, June I 2005
|
|
---|---|---|
Page(s) | 781 - 798 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20041850 | |
Published online | 13 May 2005 |
Multi-object spectroscopy of low redshift EIS clusters
III. Properties of optically selected clusters
1
Copenhagen University Observatory, Juliane Maries Vej 30, 2100 Copenhagen, Denmark e-mail: lisbeth@astro.ku.dk
2
Observatoire de la Côte d'Azur, Laboratoire Cassiopée, BP 4229, 06304 Nice Cedex 4, France
3
European Southern Observatory, Karl-Schwartzschild-Str. 2, 85748 Garching b. München, Germany
Received:
16
August
2004
Accepted:
14
January
2005
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 . We have now obtained spectroscopic
redshifts for 34 EIS cluster candidates with
(see also Hansen et al. 2002, A&A, 388, 1; Olsen et al. 2003, A&A, 409, 439). Of those we
spectroscopically confirm 32 with redshifts ranging from
to 0.283. We find that: 1) the velocity dispersions of the
systems range from
km s-1 to
km s-1, typical of galaxy groups to rich
clusters; 2) richnesses corresponding to Abell classes
;
and 3) concentration indices ranging from
to
. From
the analysis of the colours of the galaxy populations we find that 60% 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.
Key words: galaxies: clusters: general / cosmology: observations / galaxies: distances and redshifts / galaxies: photometry
© ESO, 2005
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