THE NATURE OF FOSSIL GROUPS: CLUES TO THEIR ORIGIN

The main objective of this program is to test the possibility that a fossilgroup is the endproduct of the merging of dense groups/poor clusters. Fossilgroups exhibit an extended Xray halo with LX, total mass and gas mass similarto poor clusters, but optically they are dominated by a single luminouselliptical galaxy surrounded by faint companions. We plan to obtain XMMNewtondata to analyse the diffuse emission of two fossils groups selected from theSDSS and ROSAT databases. We will determine their masses, M/L, measure theirtemperatures and metallicities and map their gas densities, in order to infertheir dynamical states. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]