A correlation between light concentration and cluster local density for elliptical galaxies

Using photometric and redshift data for the Virgo and Coma Clusters, we present evidence for a correlation between the light concentration of elliptical galaxies (including dwarf ellipticals) and the local three-dimensional (i.e., nonprojected) density of the clusters: more concentrated ellipticals are located in denser regions. The null hypothesis (i.e., the absence of any relation) is rejected at a significance level of better than 99.9%. In order to explain the observed relation, a power law relating the galaxy light concentration and the cluster three-dimensional density is proposed. We study how the projection effects affect the form and dispersion of the data points in the light concentration-projected density diagram. The agreement between our model and the observed data suggests that there is a paucity of dwarf elliptical galaxies in the cluster central regions.