2006ApJ...641..293T

Various balloon and satellite observatories have revealed what appears to be an extended source of 0.511 MeV annihilation radiation with a flux of ∼10^–3 photons/cm2/s centered on the Galactic center. Positrons from radioactive products of stellar explosions can account for a significant fraction of the emission. We discuss an additional source for this emission: namely, e⁺e^– pairs produced when X-rays generated from the ∼2.6x10⁶ M_☉Galactic center black hole interact with ∼10 MeV temperature blackbody emission from 10¹⁷ g black holes within 10¹⁴-10¹⁵ cm of the center. The number of such small-mass black holes (SMMBHs) can account for the production of the 10⁴² e⁺/s that produces the observed annihilation in the inner Galaxy when transport effects are taken into account. We consider the possibility for confirming the presence of these SMMBHs in the Galactic center region with future generations of γ-ray instruments if a blackbody-like emission of ∼10 MeV temperature would be detected by them. SMMBHs can be a potential candidate for the dark (invisible) matter halo.