The fundamental plane of cluster ellipticals

Abstract

It is shown that, for the Coma cluster ellipticals of normal surface brightness, there is a highly significant correlation between the residual from the D n -σ relation and effective surface brightness μ. The higher surface brightness ellipticals give systematically larger D n -σ distances. New, independent V-band photometry, when combined with the published velocity dispersion data, also show the same, highly significant correlation. This correlation arises because, for the Coma ellipticals, D n does not give a precise edge-on view of the fundamental plane. The Coma ellipticals with μ < 22.0 define a fundamental plane with no intrinsic scatter, indicating a remarkable degree of homogeneity