How Were Cold Fronts Formed in Abell 496?
Raymond White (University of Alabama) , Renato Dupke (University of Michigan), Joel Bregman (University of Michigan)
Cold fronts, discontinuities in X-ray surface brightness accompanied by continuous gas pressure distributions, are often found in relaxed galaxy clusters. Explaining cold fronts as remnant cores of head-on subcluster mergers does not generally work for such clusters, which has led to competing models invoking gas sloshing. We use a deep Chandra exposure of Abell 496 to test predictions of these sloshing models by analyzing the spatial distributions of density, temperature, metal abundances and abundance ratios. We confirm that the temperature and chemical discontinuities in this cluster are not consistent with being directly identified with a core merger remnant. Nonetheless, we find that these structures could have been caused by sloshing induced by an off-center collision with a dark matter halo. We find a relatively cool "arm" of gas, with different abundance ratios than its surroundings, stretching from the central regions. The spiral shape of this arm emanating from the center is reminiscent of structures induced by off-center encounters with less massive dark matter halos, as found in recent numerical simulations of Ascasibar and Markevitch (2006).