Resonant Friction on Disks in Galactic Nuclei

Abstract We argue that resonant friction has a dramatic effect on a disk whose rotation direction is misaligned with that of its host nuclear star cluster. The disk’s gravity causes gravitational perturbation of the cluster that in turn exerts a strong torque back onto the disk. We argue that this torque may be responsible for the observed disruption of the clockwise disk of young stars in the Galactic center, and show in numerical experiments that it produces the observed features in the distribution of the stars’ angular momenta. More generally, we speculate that the rotation of nuclear star clusters has a stabilizing effect on the orientation of transient massive accretion disks around the supermassive black holes residing in their centers, and thus on the directions and magnitudes of the black hole spins.