Seeding Supermassive Black Holes with Self-Interacting Dark Matter: A
  Unified Scenario with Baryons
  Observations show that supermassive black holes (SMBHs) with a mass of
$\sim10^9 M_\odot$ exist when the Universe is just $6\%$ of its current age. We
propose a scenario where a self-interacting dark matter halo experiences
gravothermal instability and its central region collapses into a seed black
hole. The presence of baryons in protogalaxies could significantly accelerate
the gravothermal evolution of the halo and shorten collapse timescales. The
central halo could dissipate its angular momentum remnant via viscosity induced
by the self-interactions. The host halo must be on high tails of density
fluctuations, implying that high-$z$ SMBHs are expected to be rare in this
scenario. We further derive conditions for triggering general relativistic
instability of the collapsed region. Our results indicate that self-interacting
dark matter can provide a unified explanation for diverse dark matter
distributions in galaxies today and the origin of SMBHs at redshifts
$z\sim6-7$.
