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.
I have been leading the effort to study in detail a newly discovered dissociative galaxy cluster merger (DLSCL J0916.2+2951* a.k.a the Musket Ball Cluster), were the collisionless dark matter (blue, in the figure below) and galaxies have become separated from the collisional cluster gas (red, in the figure below). To date only 5 dissociative mergers have been confirmed, the most famous being the Bullet Cluster. These dissections of the cosmos are proving to be some of the best laboratories for studying dark matter.
*This unattractive name refers to the fact that it was discovered in the Deep Lens Survey, is a cluster, and where it is located. Our team affectionately calls it the Musket Ball Cluster since it is similar to the Bullet Cluster yet older and slower.