In reality most stars in the mergers were formed long before the collisions. Apparently these models are currently incomplete. By observing distant galaxies astronomers look back in time. The colliding galaxies are at a distance of roughly 8 billion light years. This means it took 8 billion years before their light reached the Earth.
Most mergers are in the outskirts of the cluster.
The large number of mergers in this cluster is likely related to the fact that the cluster is still in the process of formation. The collisions are probably taking place in small clumps which are not yet fully integrated into the cluster. Simulations show that this collision will lead to the formation of an elliptical galaxy. It is the most important chapter of the thesis of Peter van Dokkum. The discovery is the most important chapter of the thesis of Peter van Dokkum.