A deep Chandra observation of Abell 4059:: A new face to radio-mode'' AGN feedback?

A deep Chandra observation of the cooling core cluster Abell 4059 (A4059) is presented. Previous studies have found two X-ray cavities in the central regions of A4059 together with a ridge of X-ray emission 20 kpc southwest of the cluster center. These features are clearly related to the radio galaxy PKS 2354-35, which resides in the cD galaxy. Our new data confirm these previous findings and strengthen previous suggestions that the southwestern ridge is colder and denser than, but in approximate pressure equilibrium with, the surrounding ICM atmosphere. In addition, we find evidence for a weak shock that wraps around the north and east sides of the cavity structure. Our data allow us to map the two-dimensional (2D) distribution of metals in the ICM of A4059 for the first time. We find that the southwest ridge possesses an anomalously high (supersolar) metallicity. The unusual morphology, temperature structure, and metal distribution all point to significant asymmetry in the ICM atmosphere prior to the onset of radio galaxy activity. Motivated by the very high metallicity of the southwest ridge, we hypothesize that the ICM asymmetry was caused by the extremely rapid stripping of metal-enriched gas from a starburst galaxy that plunged through the core of A4059. Furthermore, we suggest that the onset of powerful radio galaxy activity in the cD galaxy may have been initiated by this starburst/stripping event, via either the tidal shocking of cold gas native to the cD galaxy or the accretion of cold gas that had been stripped from the starburst galaxy.