Chandra observations of A85: Merger of the south subcluster

We present an analysis of a highly asymmetric cluster merger from a Chandra observation of A85. The merger shows significant disruption of the less massive subcluster from ram pressure effects. Nevertheless, a cold core, coincident with the cD galaxy, is observed to persist in the subcluster. We derive dynamical information from the motion of the cold core through the main cluster's intracluster medium. Multiple derivations of the velocity of the core suggest a Mach number of script M sign ≈ 1.4, or v ∼ 2150 km s ^-1, although with substantial uncertainty. We construct a consistent kinematic model for the merger based on this dynamical analysis. As has been found for other such "cold fronts," conduction appears to be suppressed across the front. Thermal conduction may be suppressed by a magnetic field with a significant component perpendicular to the subcluster's direction of motion. The effect of the merger interaction in creating and shaping the observed radio sources is also discussed. It appears most likely that the radio source is due to distorted and detached lobes from the subcluster cD galaxy, rather than being a radio halo.