Surface brightness profile of NGC 3311 in the r band (black line) and the radially averaged globular cluster number density profile (red line), arbitrarily shifted to match the surface brightness. The left panel shows the cluster-centric distance on a linear scale, and the right panel uses a log scale. The shaded areas indicate the three regimes observed in the GC number density profile: (I) where incompleteness effects are significant, (II) where the GCs follow the galaxy light, and (III) where the GCs trace the ICL. Region I is also shaded in the left panel for reference. At distances larger than ∼6 arcmin from the centre, the shallower profiles indicate the contribution of the ICL baryons, i.e. diffuse light plus intra-cluster GCs.