Phase-space diagram for the stacked member galaxy data of the clusters in the WH15 catalogue. The top panel shows the diagram before the correction procedure, while the bottom panel shows the background-corrected phase-space diagram. The colour bar shows the number of member galaxies we have in each bin. The bins have a size of 0.05 r₅₀₀ × 50 km s⁻¹. The vertical dashed red lines show the bins where we calculated the mean of the velocity distributions.