MACS0025: playing cluster billiards with gravity

Anja Von Der Linden, KIPAC, Stanford University

We present a joint X-ray, strong and weak lensing analysis of the merging cluster MACSJ0025.4-1222. MACS0025 consists of two merging sub-clusters of similar richness at z=0.586. The peak of the X-ray emission does not coincide with either galaxy overdensity, but is centered between them. A gravitational lensing analysis using both strong and weak lensing reveals two mass clumps, coinciding with the galaxy overdensities. Thus, dark matter and hot gas are clearly displaced in this system. This is analogous to the geometry of the Bullet Cluster (1E0657-56), apart from the absence of a cold, dense core (a `Bullet') in MACS0025. Under the assumption that the subclusters experienced a head-on collision in the plane of the sky, we obtain a rough limit on the dark matter self-interaction cross-section of sigma/m < 4 cm^2/g, re-affirming the results from the Bullet Cluster on the collisionless nature of dark matter.