Triaxial galaxies containing massive black holes or central density cusps

Abstract

The stability of box orbits of stars in triaxial galaxies is investigated. The box orbits in such galaxies carry stars arbitrarily close to the center. The effects on such orbits are investigated for two cases: where a massive black hole lurks at the center and where the stellar density becomes arbitrarily large near the center. Over a Hubble time, a central black hole with 2 percent of the core mass will disrupt most box orbits with apocenters interior to about 1 kpc, leading possibly to an abrupt loss of triaxiality throughout the galaxy. A simple calculation suggests, however, that the loss of triaxiality will be confined to the center.