Gamma-ray evidence for dark matter clumps

We discuss the possibility of identification of point-like gamma-ray sources (PGS) with small-scale dark matter (DM) clumps in our Galaxy. Gamma rays are supposed to originate from annihilation of DM particles in the clumps, where the annihilation rate is supposed to be enhanced, besides higher density, due to smaller relative velocities v of DM particles. We parametrized the annihilation cross section σann(v) in the form of an arbitrary power-law dependence on the relative velocity v with/without the Sommerfeld-Gamow-Sakharov factor, implying the existence of a new Coulomb-like interaction. Adopting different parameters of the cross-section and the clump, satisfying the condition Ω ≲ 0.2 on the density of DM particles, they are constrained by comparison with the Fermi/LAT data on unidentified PGS as well as on diffuse γ radiation; the results are applied to concrete DM candidates. This analysis is found to be sensitive enough to the existing uncertainty in the DM density profiles in the clump, which can provide a tool for their test. We also discuss the possibilities where a gamma-radiating clump changes visibly its position on the celestial sphere and it is seen as a spatially extended gamma source (EGS), which can be probed in future experiments like Gamma-400.