Residual background fluctuations, R_lim and S/N estimate. Top panels: intensity profiles for HCG 86A (left panel) and HCG 86C (right panel) in the g and r bands. The two vertical dashed lines show the estimated value for R_lim for each band and the horizontal lines indicate the average value of the residual background fluctuations in each band. Bottom panels: S/N profiles for HCG 86A (left panel) and HCG 86C (right panel) in the g (blue points) and r (green points) bands. The vertical dashed lines indicate the R_lim for each band and the horizontal lines indicate the zero value for signal to noise ratio. The bump observed at ∼1000−2000 pixels, in both g and r profiles centred on the HCG 86C, reasonably corresponds to the IGL contribution around the core of the group.