Gravitational Encounters and the Evolution of Galactic Nuclei. IV. Captures Mediated by Gravitationalwave Energy Loss
Abstract
Direct numerical integrations of the twodimensional FokkerPlanck equation are carried out for compact objects orbiting a supermassive black hole at the center of a galaxy. As in Papers IIII, the diffusion coefficients incorporate the effects of the lowestorder postNewtonian corrections to the equations of motion. In addition, terms describing the loss of orbital energy and angular momentum due to the 5/2order postNewtonian terms are included. In the steady state, captures are found to occur in two regimes that are clearly differentiated in terms of energy, or semimajor axis; these two regimes are naturally characterized as “plunges” (low binding energy) and “EMRIs,” or extrememassratio inspirals (high binding energy). The capture rate, and the distribution of orbital elements of the captured objects, are presented for two steadystate models based on the Milky Way: one with a relatively high density of remnants and one with a lower density. In both models, but particularly in the second, the steadystate \bar{f}(E) and the distribution of orbital elements of the captured objects are substantially different than if the BahcallWolf energy distribution were assumed. The ability of classical relaxation to soften the blocking effects of the Schwarzschild barrier is quantified. These results, together with those of Papers IIII, suggest that a FokkerPlanck description can adequately represent the dynamics of collisional loss cones in the relativistic regime.
 Publication:

The Astrophysical Journal
 Pub Date:
 November 2015
 DOI:
 10.1088/0004637X/814/1/57
 arXiv:
 arXiv:1511.08169
 Bibcode:
 2015ApJ...814...57M
 Keywords:

 black hole physics;
 galaxies: kinematics and dynamics;
 galaxies: nuclei;
 Astrophysics  Astrophysics of Galaxies;
 General Relativity and Quantum Cosmology
 EPrint:
 14 pages, 10 figures