Can annihilating Dark Matter be lighter than a few GeVs?
  We estimate the gamma ray fluxes from the residual annihilations of Dark Matter particles having a mass mdm \in [MeV, O(GeV)] and compare them to observations. We find that particles lighter than O(100 MeV) are excluded unless their cross section is S-wave suppressed. 
C. Boehm, T.A. Ensslin, J. Silk