Radial surface density distribution of sources in the reference (black histograms) and best (red histogram) samples. Panel a) all R_h values are taken. The r^1/4 fit to data is shown with gray lines. The dotted lines show the histograms without correction for areal coverage. The vertical long-dashed line is the position of limiting galactocentric radius R_bg. Panel b) as upper, but only GC candidates are plotted. The green-dashed line shows the galaxy surface brightness (from Capaccioli et al., in prep., g band, arbitrary scale). Panel c) as panel a), but for UCD candidates.