Black Holes as Dark Matter Annihilation 'Boosters'

The presence and growth of Intermediate and Supermassive Black Holes modify the surrounding distribution of stars and Dark Matter, and inevitably affect the prospects for indirectly detecting Dark Matter through its annihilation products. We show here that under specific circumstances, Black Holes can act as Dark Matter annihilation 'boosters'. In particular, we show that mini-spikes, i.e. Dark Matter overdensities around Intermediate-Mass Black Holes, would be bright sources of gamma-rays, well within the reach of the space telescope GLAST, that can be discriminated from ordinary astrophysical sources thanks to their peculiar energy spectrum and spatial distribution