The Structure of Brightest Cluster Members. II. Mergers

Surface photometry of 342 bright elliptical galaxies in 103 clusters is analyzed for evidence of mergers. Structural differences between brightest cluster members (BCMs) and normal ellipticals can be summarized as having enlarged characteristic radii and shallow profile slopes (beta greater than -1.7). Profile morphology criteria for the elliptical types gE, D, and cD are outlined. Comparison of observations with numerical simulations of mergers strongly suggests a past history of dynamical growth for BCMs. Weak correlations of global cluster properties to BCMs supports the hypothesis proposed by Merritt (1984) that mergers are important in early subgroups before virialization and formation of a cluster identity.