Triaxial Black-Hole Nuclei

Abstract

We demonstrate that the nuclei of galaxies containing supermassive black holes can be triaxial in shape. Schwarzschild's method was first used to construct self-consistent orbital superpositions representing nuclei with axis ratios of 1:0.79:0.5 and containing a central point mass representing a black hole. Two different density laws were considered, with power-law slopes of -1 and -2. We constructed two solutions for each power law: one containing only regular orbits and the other containing both regular and chaotic orbits. Monte-Carlo realizations of the models were then advanced in time using an N-body code to verify their stability. All four models were found to retain their triaxial shapes for many crossing times. The possibility that galactic nuclei may be triaxial complicates the interpretation of stellar-kinematical data from the centers of galaxies and may alter the inferred interaction rates between stars and supermassive black holes.