MERGER HYDRODYNAMICS OF THE LUMINOUS CLUSTER RX J1347.5–1145

Abstract

ABSTRACT We present an analysis of the complex gas hydrodynamics in the X-ray-luminous galaxy cluster RX J1347.5–1145 caught in the act of merging with a subcluster to its southeast using a combined 186 ks Chandra exposure, 2.5 times greater than previous analyses. The primary cluster hosts a sloshing cold front spiral traced by four surface brightness edges west, southeast, east, and northeast from the primary central dominant galaxy, suggesting that the merger is in the plane of the sky. We measure temperature and density ratios across these edges, confirming that they are sloshing cold fronts. We observe the eastern edge of the subcluster infall shock, confirming that the observed subcluster is traveling from the southwest to the northeast in a clockwise orbit. We measure a shock density contrast of and infer a Mach number of 1.25 ± 0.08 and a shock velocity of km s−1. Temperature and entropy maps show cool, low-entropy gas trailing the subcluster in a southwestern tail, consistent with core shredding. Simulations suggest that a perturber in the plane of the sky on a clockwise orbit would produce a sloshing spiral winding counterclockwise, opposite to that observed. The most compelling solution to this discrepancy is that the observed southeastern subcluster is on its first passage, shock-heating gas during its clockwise infall, while the main cluster’s clockwise cold front spiral formed from earlier encounters with a second perturber orbiting counterclockwise.