The Effect of Stars on the Dark Matter Spike Around a Black Hole: A Tale of Two Treatments

Understand

We revisit the role that gravitational scattering off stars plays in establishing the steady-state distribution of collisionless dark matter (DM) around a massive black hole (BH).

• This is a physically interesting problem that has potentially observable signatures, such as $\gamma-$rays from DM annihilation in a density spike.
• The system serves as a laboratory for comparing two different dynamical approaches, both of which have been widely used: a Fokker-Planck treatment and a two-component conduction fluid treatment.
• In our Fokker-Planck analysis we extend a previous analytic model to account for a nonzero flux of DM particles into the BH, as well as a cut-off in the distribution function near the BH due to relativistic effects or, further out, possible DM annihilation.