Surface-brightness radial slopes taken from Table 1. The dark blue area corresponds to the expected values in a non-perturbed system according to the present numerical investigation. The light-blue area is the same, but for edge-on discs, taking into account the potential nonresolution of the disc in the vertical direction. For some systems, there are different slope estimates depending on the radial position in the halo and on which side of the disc has been considered. In this case, up to four values are displayed: diamonds and cross symbol signify the radial indexes in the inner- and outer halo, respectively, for one disc side, and the squares and plus symbol are the equivalent indexes for the opposite side. For systems where there is only one global fitted radial index, all four symbols do overlap. Edge-on systems are written in italics.