MULTICOLOR SURFACE PHOTOMETRY OF BRIGHTEST CLUSTER GALAXIES .2. ENLARGING THE SAMPLE AND IMPROVING THE ANALYSIS

Intrinsic color profiles of a sample of nine Brightest Cluster Galaxie s (BCGs) are recovered from the observed color profiles by evaluating spurious gradients introduced by errors in the determination of the sk y levels and by different seeing conditions between the observations. Isophote shapes and surface brightness profiles are presented for the four newly observed BCGs. Three out of nine BCGs show color gradients of the order of 0.10 mag per decade in radius. Five BCGs do not posses s any color gradient larger than 0.01 mag per decade in radius. We. do not see any correlation between the presence (or the sign) of a color gradient and the BCG morphology (slope and shape of its surface brigh tness profile), or the cluster richness. This argues against a strong and recent influence of the environment on the BCG morphology. The slo pe of the BCG surface brightness profile is correlated to the cluster richness, posing a constraint on the initial conditions, or on the phy sical mechanism that is responsible for the present BCG morphology. Fi nally, only one BCG can be a cD despite visual classification as such of all studied BCGs.