A&A 379, 35-45 (2001)
DOI: 10.1051/0004-6361:20011237
Radio-optically selected clusters of galaxies
II. The cluster sample
A. Zanichelli1, R. Scaramella2, G. Vettolani1, M. Vigotti1, S. Bardelli3 and G. Zamorani31 Istituto di Radioastronomia -CNR, Via Gobetti 101, 40129 Bologna, Italy
2 Osservatorio Astronomico di Roma, via Osservatorio 2, 00040 Monteporzio Catone (RM), Italy
3 Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
(Received 13 December 2000 / Accepted 6 August 2001)
Abstract
We present a sample of 171 candidate groups and clusters of galaxies at
intermediate redshift over an area of
550 sq degrees at the South
Galactic Pole, selected by using optically identified radio sources from the
NRAO VLA Sky Survey as tracers of dense environments.
Out of these 171 candidates, 76 have a counterpart in the literature while
95 of them are previously unknown clusters.
This paper presents the cluster selection technique, based on the search of
excesses in the optical surface density of galaxies near identified
radiogalaxies, and the first spectroscopic results aimed to confirm the
presence of a cluster.
Spectroscopy for 11 candidates led to the detection of 9 clusters at a
redshift in the range
, with estimated velocity dispersions
ranging from values typical of clusters to those of galaxy groups.
These results show that this technique represents a powerful tool for the
selection of homogeneous samples of intermediate redshift clusters over a wide
range of richness.
Key words: catalogs -- radio continuum: galaxies -- galaxies: clusters: general -- cosmology: observations
Offprint request: A. Zanichelli, azanichelli@ira.bo.cnr.it
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