Understanding the Physics and Observational Effects of Collisions between Galaxy Clusters

Galaxy clusters, the largest gravitationally bound objects in the universe, form over time from collisions and mergers between clusters and between clusters and smaller galaxy groups. The results of these collisions can be detected in a variety of ways. In one case, I have found that clusters which have recently undergone a merger will have an enhanced Sunyaev-Zel’dovich (SZ) Effect. The SZ signal from thousands of clusters will soon be measured in order to constrain the dark matter and dark energy content of the universe. However, I have shown that while observations of the central SZ effect, which is more sensitive to merger enhancements, will hopelessly bias these estimates, the integrated SZ signal will not and should be the quantity extracted from SZ surveys. Another result of cluster mergers is the acceleration of relativistic particles, which produce non-thermal emission that should be observable in X-rays. In the Coma cluster, the brightest merging cluster in the sky, detections of this emission have been claimed, though these findings are controversial. Using observations of Coma with the Hard X-ray Detector onboard Suzaku, I find no conclusive non-thermal emission and derive an upper limit on the emission that excludes the most recent previous detection.