The fundamental plane of cluster ellipticals

We show, that for the Coma cluster ellipticals of normal surface brightness, there is a highly significant correlation between the residual from the Dn-σ relation and effective surface brightness μe(B). The higher surface brightness ellipticals give systematically larger Dn-θ 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, Dn does not give a precise edge-on view of the fundamental plane. The Coma ellipticals with μe(B) < 22.0 define a fundamental plane with no intrinsic scatter, indicating a remarkable degree of homogeneity. (Author)