Indirect search for dark matter: prospects for GLAST

Possible indirect detection of neutralino, through its γ-ray annihilation product, by the forthcoming GLAST satellite from our galactic halo, M31, M87 and the dwarf galaxies Draco and Sagittarius is studied. γ-ray fluxes are evaluated for the two representative energy thresholds, 0.1 GeV and 1 GeV, at which the spatial resolution of GLAST varies considerably. Apart from dwarfs which are described here by tidally-truncated King’s profiles, fluxes are compared for halos with central cusps and cores. It is demonstrated that substructures irrespective of their profiles enhance the γ-ray flux only marginally. The expected γ-ray intensity above 1 GeV at high galactic latitudes is consistent with the residual emission derived from EGRET data if the density profile has a central core, whereas for a central cusp only a substantial enhancement would explain the observations. The flux from M31 can be detected above 0.1 GeV by GLAST, even if its halo has a core profile, but only if the neutralino mass is less than 20 GeV. For Sagittarius, the flux above 0.1 GeV is detectable by GLAST provided the neutralino mass is below 50 GeV. The fluxes from M87 and Draco are always below the sensitivity limit of GLAST. However, the presence of a supermassive black hole in a central cusp would lead to a detectable signal from M87 and a significantly enlarged detectable neutralino mass range for M31.