Suzaku Observations of the X-ray Brightest Fossil Group ESO 3060170

Abstract

"Fossil" galaxy groups, each dominated by a relatively isolated giant elliptical galaxy, have many properties intermediate between groups and clusters of galaxies. We used the {\sl Suzaku} X-ray observatory to observe the X-ray brightest fossil group, ESO 3060170, out to $R_{200}$, in order to better elucidate the relation between fossil groups, normal groups, and clusters. We determined the intragroup gas temperature, density, and metal abundance distributions and derived the entropy, pressure and mass profiles for this group. The entropy and pressure profiles in the outer regions are flatter than in simulated clusters, similar to what is seen in observations of massive clusters. This may indicate that the gas is clumpy and/or the gas has been redistributed. Assuming hydrostatic equilibrium, the total mass is estimated to be $\sim1.7\times10^{14}$ $M_{\odot}$ within a radius $R_{200}$ of $\sim1.15$ Mpc, with an enclosed baryon mass fraction of 0.14. The integrated iron mass-to-light ratio of this fossil group is larger than in most groups and comparable to those of clusters, indicating that this fossil group has retained the bulk of its metals. A galaxy luminosity density map on a scale of 25 Mpc shows that this fossil group resides in a relatively isolated environment, unlike the filamentary structures in which typical groups and clusters are embedded.