EDP Sciences
Free access
Volume 379, Number 1, November III 2001
Page(s) 21 - 34
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20011236

A&A 379, 21-34 (2001)
DOI: 10.1051/0004-6361:20011236

Radio-optically selected clusters of galaxies

I. The radiogalaxy sample
A. Zanichelli1, M. Vigotti1, R. Scaramella2, G. Grueff3 and G. Vettolani1

1  Istituto di Radioastronomia -CNR, Via Gobetti 101, 40129 Bologna, Italy
2  Osservatorio Astronomico di Roma, via Osservatorio 2, 00040 Monteporzio Catone (RM), Italy
3  Dipartimento di Fisica, Università di Bologna, Via Irnerio 46, 40127 Bologna, Italy

(Received 13 December 2000 / Accepted 6 August 2001 )

In order to study the status and the possible evolution of clusters of galaxies at intermediate redshifts ($z \sim$ 0.1-0.3), as well as their spatial correlation and relationship with the local environment, we built a sample of candidate groups and clusters of galaxies using radiogalaxies as tracers of dense environments. This technique -complementary to purely optical or X-ray cluster selection methods -represents an interesting tool for the selection of clusters in a wide range of richness, so to make it possible to study the global properties of groups and clusters of galaxies, such as their morphological content, dynamical status and number density, as well as the effect of the environment on the radio emission phenomena. In this paper we describe the compilation of a catalogue of ~16 000 radio sources in the region of the South Galactic Pole extracted from the publicly available NRAO VLA Sky Survey maps, and the optical identification procedure with galaxies brighter than bJ = 20.0 in the EDSGC Catalogue. The radiogalaxy sample, valuable for the study of radio source populations down to low flux levels, consists of 1288 identifications and has been used to detect candidate groups and clusters associated to NVSS radio sources. In a companion paper we will discuss the cluster detection method, the cluster sample as well as first spectroscopic results.

Key words: catalogs -- radio continuum: galaxies -- galaxies: clusters: general -- cosmology: observations

Offprint request: A. Zanichelli, azanichelli@ira.bo.cnr.it

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