Velocity dispersion estimates of APM galaxy clusters.

ALONSO, M. VICTORIA; VALOTTO, CARLOS; LAMBAS, DIEGO G.; MURIEL, HERNÁN

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 1999 vol. 308 p. 618 - 622

0035-8711

We present 83 new galaxy radial velocities in the field of 18 APM clusters with redshifts between 0.06 and 0.13. The clusters have Abell identifications and the galaxies were selected within 0.75h^-1Mpc in projection from their centres. We derive new cluster velocity dispersions for 13 clusters using our data and published radial velocities. We analyse correlations between cluster velocity dispersions and cluster richness counts as defined in Abell and APM catalogues. The correlations show a statistically significant trend although with a large scatter, suggesting that richness is a poor estimator of cluster mass irrespectively of cluster selection criteria and richness definition. We find systematically lower velocity dispersions in the sample of Abell clusters that do not fulfil APM cluster selection criteria, suggesting artificially higher Abell richness counts owing to contamination by projection effects in this subsample.