Structure of Brightest Cluster Galaxies and Intracluster Light

Observations of 170 local (z 31 g' mag arcsec$^{-2}$ by large dithering and subtraction of night-sky flats. Residual background inhomogeneities brighter than SB<27.6 g' mag arcsec$^{-2}$ caused by galactic cirrus are detected in front of 23% of the clusters. Accretion signatures appear in form of tidal streams in 22%, shells in 9.4%, multiple nuclei in 47% and two Brightest Cluster Galaxies (BCGs) in 7% of the clusters/BCGs. We measure SB profiles of the BCGs and their surrounding Intracluster Light (ICL) down to a limiting SB of 30 g' mag arcsec$^{-2}$. We find that 71% of the BCG+ICL systems have SB profiles that are well described by a single Sersic (SS) function whereas 29% require a double Sersic (DS) function to obtain a good fit. SS BCGs, having more symmetric isophotal shapes and fewer detected accretion signatures than DS BCGs, appear to have slightly more relaxed morphology than their DS counterparts. We argue that the outer Sersic component is unlikely to trace the dynamically hot ICL. We find that BCGs have scaling relations that differ markedly from those of normal ellipticals, likely due to their indistinguishable embedding in the ICL. The most extended BCG+ICL systems have luminosities and radii comparable to whole clusters. On average, the ICL is better aligned than the BCG with the host cluster in position angle and centering. That makes it a potential Dark Matter tracer. We find positive correlations between BCG+ICL brightness and cluster mass, -radius, -richness and integrated satellite brightness, confirming that BCG/ICL growth is indeed coupled with cluster growth.