Growth of black holes and dark matter accretion

Abstract

We investigate the distribution of fermion dark matter in the Milky Way galaxy and find that dark matter could gravitationally condensate in a degenerate core of mass of 3 × 106Mȯ embedded in a dark matter halo of 3 × 1012Mȯ with a size of about 200 kpc. We then show that the galactic black hole of mass of about 3 × 106Mȯ might have grown from a stellar seed black hole by mainly accreting dark matter from the compact degenerate fermion core. This leads to a lower limit on the mass of the fermion dark matter of about (6–10) keV. It is then argued that the constrained dark matter could be a sterile neutrino.