A Symbiotic Scenario for the Rapid Formation of Supermassive Black Holes
  The most massive black holes, lurking at the centers of large galaxies, must have formed less than a billion years after the big bang, as they are visible today in the form of bright quasars at redshift larger than six. Their early appearance is mysterious, because the radiation pressure, generated by infalling ionized matter, inhibits the rapid growth of these black holes from stellar-mass black holes. Here we show that the supermassive black holes may form timeously through the accretion of radiationless and densely packed neutrino dark matter onto stellar-mass black holes. Our symbiotic scenario relies on the formation of, first, supermassive degenerate sterile neutrino balls through gravitational cooling and, then, stellar-mass black holes through supernova explosions of massive stars at the center of the neutrino balls. The observed lower and upper limits of the supermassive black holes are explained by the corresponding mass limits of the preformed neutrino balls. 
M.C. Richter, G.B. Tupper and R.D. Viollier