Riding the wake of a merging galaxy cluster


E-mail: bcanning@ast.cam.ac.uk


Using William Herschel Telescope (WHT) Optically Adaptive System for Imaging Spectroscopy (OASIS) integral field unit observations, we report the discovery of a thin plume of ionized gas extending from the brightest cluster galaxy (BCG) in Abell 2146 to the subcluster X-ray cool core which is offset from the BCG by 37 kpc. The plume is greater than 15 kpc long and less than 3 kpc wide. This plume is unique in that the cluster it is situated in is currently undergoing a major galaxy cluster merger. The BCG is unusually located behind the X-ray shock front and in the wake of the ram-pressure-stripped X-ray cool core, and evidence for recent disruption to the BCG is observed. We examine the gas and stellar morphology, the gas kinematics of the BCG and their relation to the X-ray gas. We propose that a causal link between the ionized gas plume and the offset X-ray cool core provides the simplest explanation for the formation of the plume. An interaction or merger between the BCG and another cluster galaxy is probably the cause of the offset.