A Correlation between Light Concentration and Cluster Local Density for Elliptical Galaxies

Using photometric and redshift data for the Virgo and Coma clusters, wepresent evidence for a correlation between the light concentration ofelliptical galaxies (including dwarf ellipticals) and the local 3-D (i.e.non-projected) density of the clusters: more concentrated ellipticals arelocated in denser regions. The null hypothesis (i.e. the absence of anyrelation) is rejected at a significance level better than 99.9%. In order toexplain the observed relation, a power law relating the galaxy lightconcentration and the cluster 3-D density is proposed. We study how theprojection effects affect the form and dispersion of the data-points in thelight concentration-projected density diagram. The agreement between our modeland the observed data suggests that there is a paucity of dwarf ellipticalgalaxies in the cluster central regions.Comment: 7 pages, 2 figures, ApJL accepte