Subaru Weak Lensing Study of Seven Merging Clusters: Distributions of Mass and Baryons

We present and compare projected distributions of mass, galaxies, and the intracluster medium (ICM) for a sample of merging clusters of galaxies based on the joint weak-lensing, optical, and X-ray analysis. Our sample comprises seven nearby Abell clusters (0.0542≤ z≤0.279), for which we have conducted systematic, deep imaging observations with Suprime-Cam on Subaru telescope. Our seven target clusters, representing various merging stages and conditions, allow us to investigate in details the physical interplay between dark matter, ICM, and galaxies associated with cluster formation and evolution. A1750 and A1758 are binary systems consisting of two cluster-sized components, A520, A754, A1758, and A1914 are on-going cluster mergers, and A2034 and A2142 are cold-front clusters. In the binary clusters, which are presumably in an early phase of mergers, the projected mass, optical light, and X-ray distributions are overall similar and regular without significant substructures. On-going merging clusters, on the other hand, reveal highly irregular mass distributions. Overall the mass distribution appears to be similar to the galaxy luminosity distribution, whereas their distributions are quite different from the ICM distribution in a various ways. The cold front clusters also reveal irregular mass structures that differ from ICM structures. In particular, all of three cold fronts are found to be associated with a mass substructure located ahead of the moving cold front, as found in the bullet cluster 1E0657-56. We also measured for individual targets the global cluster parameters such as the cluster mass, the mass-to-light ratio, and the ICM temperature. A comparison of the ICM and virial temperatures of merging clusters from X-ray and weak-lensing analyses, respectively, shows that the ICM temperature of on-going and cold-front clusters is significantly higher than the cluster virial temperature by a factor of 2−3. This temperature excess in the ICM can be explained by the effects of merger boosts. Our results show the temperature excess in merging clusters is independent of the cluster mass, indicating that the energy release from mergers is determined not only by the cluster mass but also by other merging parameters.