We were just awarded a grant from UC-HiPACC to establish a UC Davis - UC Irvine collaboration to study merging clusters, with the directive of determining the nature of dark matter. Dark Matter is one of the great outstanding mysteries.  Although still in its infancy, the study of merging galaxy clusters has been shown to be one of the best means of determining the nature of dark matter.  However to realize this potential requires a concerted effort on the part of astronomers and computational theorist, due to necessity to compare simulations and observations of real systems. 

Copied from Chandra press release.

Using a combination of powerful observatories in space and on the ground, astronomers have observed a violent collision between two galaxy clusters in which so-called normal matter has been wrenched apart from dark matterthrough a violent collision between two galaxy clusters.

The newly discovered galaxy cluster is called DLSCL J0916.2+2951. It is similar to the Bullet Cluster, the first system in which the separation of dark and normal matter was observed, but with some important differences. The newly discovered system has been nicknamed the "Musket Ball Cluster" because the cluster collision is older and slower than the Bullet Cluster.