Effects of AGN and mergers on the cores of galaxy groups

Using a sample of 12 galaxy groups observed by XMM-Newton and Chandra, we examine the effects of AGN heating and mergers on group properties and structure. While some systems possess clearly disturbed surface brightness features (e.g. cavities), in others high resolution temperature and abundance maps are required to reveal structure indicative of interactions. Comparison between the five systems with strongly disturbed cores and the more relaxed members of the sample suggests that central entropy and cooling time are only affected by the most powerful AGN activity. However, the mass-to-light ratio in the core of some systems drops below that expected for stars alone, suggesting that even in apparently relaxed groups AGN activity may push the gas out of hydrostatic equilibrium.