EGRET EXCESS OF DIFFUSE GALACTIC GAMMA RAYS AS A TRACE OF THE DARK MATTER HALO

摘要

The diffuse Galactic gamma ray data, which were measured by the EGRET experiment, show a clear excess for energies above 1 GeV in comparison with the expectations from conventional Galactic models. The excess is seen with a similar energy spectrum in all sky directions, as expected for Dark Matter (DM) annihilation. The spectral shape of the excess is used to limit the WIMP mass to the 50-100 GeV range, while its directional dependence is used to determine a halo profile, which is consistent with a triaxial isothermal halo with additional substructure of Dark Matter in the disc. The latter is strongly correlated with the ring of stars around our galaxy at a distance of 14 kpc, thought to originate from the tidal disruption of a dwarf galaxy. It is shown that this ring of DM causes the mysterious change of slope in the rotation curve at R = 1.1 R_0.