N-body simulations for testing the stability of triaxial galaxies in MOND

Abstract

We perform a stability test of triaxial models in Modified Newtonian Dynamics (MOND) using N-body simulations. The triaxial models considered here have densities that vary with r-1 in the centre and r-4 at large radii. The total mass of the model varies from 108 to 10 10 M⊙, representing the mass scale of dwarfs to medium-mass elliptical galaxies, respectively, from deep MOND to quasi-Newtonian gravity. We build triaxial galaxy models using the Schwarzschild technique, and evolve the systems for 200 Keplerian dynamical times (at the typical length-scale of 1.0 kpc). We find that the systems are virial overheating, and in quasi-equilibrium with the relaxation taking approximately 5 Keplerian dynamical times (1.0 kpc). For all systems, the change of the inertial (kinetic) energy is less than 10 per cent (20 per cent) after relaxation. However, the central profile of the model is flattened during the relaxation and the (overall) axis ratios change by roughly 10 per cent within 200 Keplerian dynamical times (at 1.0 kpc) in our simulations. We further find that the systems are stable once they reach the equilibrium state. © 2009 RAS.