Upper panel: absolute values of the line-of-sight velocity difference between neighbours and the central CIG galaxy: | Δ ν | distribution obtained by stacking 411 CIG fields within 1 Mpc field radius (black histogram), and corresponding Gaussian distribution fits for σ between 70 and 300 km s^-1 (grey curves) with the best fit (blue curve). The Gaussian fit has been made within | Δ ν | = 300 km s^-1 (vertical line) and considering the flat continuum distribution of background neighbours as a zero point (horizontal line). Lower panel: probability density function (PDF) for neighbour galaxies peaking at | Δ ν | = 0 km s^-1 over PDF for the background flat population selected in the interval 1000 < | Δ ν | < 3000 km s^-1, as a function of the distance to the central CIG galaxy. The inner 0.3 Mpc are shaded.