Chaotic Loss Cones, Black Hole Fueling and the M-Sigma Relation

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  • 14 February 2003
Abstract
In classical loss cone theory, stars are supplied to a central black hole via gravitational scattering onto low angular momentum orbits. Much higher feeding rates are possible if the gravitational potential near the black hole is non-axisymmetric and the orbits are chaotic. Motivated by recently published, self-consistent models, we evaluate stellar capture rates in triaxial nuclei. Rates are found to exceed those in collisional loss cone models by as much as several orders of magnitude and are comparable to capture rates in spherical galaxies under conditions of continuous loss cone replenishment. In a triaxial nucleus with a steep, rho~1/r^2 density cusp, feeding drops off as 1/t^1/2 as the centrophilic orbits are depopulated. The mass captured by the black hole after a given time scales as sigma^5 with sigma the stellar velocity dispersion, and the accumulated mass in 10^10 yr is of the correct order to reproduce the M-sigma relation. Stellar disruption rates at the current epoch would be greatly enhanced, as would the decay rates of binary supermassive black holes, even if only a small fraction of the stars are on chaotic orbits.

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