Suppression of stellar tidal disruption rates by anisotropic initial conditions

We compute the rate of capture of stars by supermassive black holes using a time-dependent Fokker-Planck equation with initial conditions that present a deficit of stars on low-angular-momentum orbits. One class of initial conditions has a gap in phase space created by a binary black hole, and the other class has a globally tangentially anisotropic velocity distribution. We find that for galactic nuclei that are younger than ¡0.1 the relaxation time, the flux of stars into the black hole is suppressed with respect to the steady-state value. This effect may substantially reduce the number of observable tidal disruption flares in galaxies with black hole massesM. > M 10⁷M·.