Sky distribution, and RA – velocity difference distribution for galaxies centred at the group G_gap (left panels), and PPS diagram for G_gap and its neighbourhood galaxies (right panel). Red circles denote VO galaxies, and blue triangles denote RSF galaxies. Filled symbols show group members, and empty symbols mark galaxies in the group neighbourhood. Other galaxies (blue star forming galaxies and red galaxies with stellar populations of intermediate age) are marked with grey dots.