Abundance profiles and cool cores in galaxy groups

Abstract: Using data from the Two Dimensional XMM-Newton Group Survey (2dXGS), we have examined the abundance profile properties of both cool core (CC) and non cool core (NCC) galaxy groups. The ten NCC systems in our sample represent a population which to date has been poorly studied in the group regime. Fitting the abundance profiles as a linear function of log radius, we find steep abundance gradients in cool core (CC) systems, with a slope of -0.54+/-0.07. In contrast, non cool core (NCC) groups have profiles consistent with uniform metallicity. Many CC groups show a central abundance dip or plateau, and we find evidence for anticorrelation between the core abundance gradient and the 1.4 GHz radio power of the brightest group galaxy (BGG) in CC systems. This may indicate the effect of AGN-driven mixing within the central ~0.1r_500. It is not possible to discern whether such behaviour is present in the NCC groups, due to the small and diverse sample with the requisite radio data. The lack of strong abundance gradients in NCC groups, coupled with their lack of cool core, and evidence for enhanced substructure, leads us to favour merging as the mechanism for disrupting cool cores, although we cannot rule out disruption by a major AGN outburst. Given the implied timescales, the disruptive event must have occurred within the past few Gyrs in most NCC groups.