Structure of Brightest Cluster Galaxies and Intracluster Light

I have undertaken a photometric survey of Brightest Cluster Galaxies (BCGs) and their surrounding Intracluster light (ICL) with the Wendelstein Wide Field Imager. The sample consists of 171 BCGs at low redshift (z<0.08). Special care during the background subtraction procedure allows me to measure semi-major axis surface brightness (SB) profiles of the BCG+ICL systems down to a limiting SB = 30 mag_g' arcsec^-2. That corresponds to 425+/-220 kpc semi-major axis radii. On such low SB levels, accretion signatures like tidal streams (in 22% of the BCGs) and shells (in 9.4% of the BCGs) become visible in many of the systems,   indicating that accretion as a formation channel contributes significantly to the ICL build-up in clusters. I find that 39% of the BCG+ICL systems have SB profiles that are well described by a single Sérsic (SS) function whereas 61% require a double Sérsic (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. Members of the latter type encompass   S2=66+/-28% of their total light in the outer Sérsic component. There is a wide scatter in transition radii r_x and surface brightness at the transition radii SB(r_x) between the two Sérsic components. The integrated brightnesses of the BCG+ICL systems do not correlate with S2 and only weakly with r_x and SB(r_x). That indicates that the outer Sérsic component is unlikely to trace the ICL, contrary to often taken assumption. Moreover, we confirm the existence of broken slopes in the Kormendy- and size-luminosity relations for BCGs and regular ellipticals. The slopes for BCGs are steeper than previously known. The reason is that the amount of ICL had been underestimated since the luminosity fraction at faint SBs increases with BCG+ICL brightness. We furthermore find that the ICL is on average better aligned with the host clusters than the BCG. The ICL is on average also offset towards the cluster center. That qualifies it as a potential Dark Matter tracer. We find positive correlations between BCG+ICL brightness and cluster mass, cluster radius, cluster richness and integrated satellite brightness, confirming that BCG/ICL growth is indeed coupled  
with cluster growth.