The slice in gas velocities (taken in the merger plane) for the post-merger scenario, overlapped with the X-ray surface brightness (white contours). The colourmap colour codes absolute values of velocities in the rest frame of the mass centre of the merging clusters (Coma  + NGC 4839). Arrows show the velocity vectors. The left-hand and right-hand panels show the moments before and after the apocentric passage, respectively. As the NGC 4839 group approaches the apocenter (left-hand panel), it slows. The ram pressure decreases and the tail gas falls back towards the core of the group, driven by the gravitational drag from the subcluster. Just after the apocentric passage (right-hand panel), the NGC 4839 group starts its second infall into the Coma cluster core, while the gaseous tail is moving in the opposite direction (towards the south-west). The right-hand panel shows the same time as panels (3a) and (3b) in Fig. 8.