The Two-dimensional XMM-Newton Group Survey: z < 0.012 Groups

We present the results of the two-dimensional XMM-Newton Group Survey (2dXGS), an archival study of nearby galaxy groups. In this paper we consider 11 nearby systems (z<0.012) in Mulchaey et al., which span a broad range in X-ray luminosity from 10⁴⁰ to 10⁴³ ergs s^-1. We measure the iron abundance and temperature distribution in these systems and derive pressure and entropy maps. We find statistically significant evidence for structure in the entropy and pressure of the gas component of seven groups on the 10%-20% level. The XMM-Newton data for the three groups with best statistics also suggest patchy metallicity distributions within the central 20-50 kpc of the brightest group galaxy, probed with 2-10 kpc resolution. This provides insights into the processes associated with thermalization of the stellar mass loss. Analysis of the global properties of the groups reveals a subclass of X-ray-faint groups, which are characterized by both higher entropy and lower pressure. We suggest that the merger history of the central elliptical is responsible for both the source and the observed thermodynamical properties of the hot gas of the X-ray-faint groups.