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

TL;DR

This study uses N-body simulations to test the stability of triaxial galaxy models in MOND, revealing that such systems are generally stable after relaxation, with some structural changes.

Contribution

First comprehensive N-body stability analysis of triaxial galaxies in MOND across various mass scales and density profiles.

Findings

Systems reach quasi-equilibrium within 5 dynamical times.

Inertial energy changes less than 10%, kinetic energy less than 20%.

Central profiles flatten and axis ratios change by about 10%.

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 center and $r^{-4}$ at large radii. The total mass of the model varies from $10^8\Msun$ to $10^{10}\Msun$, 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% (20%) after relaxation. However, the central profile of the model is flattened during the relaxation and the (overall) axis ratios change by roughly 10% within 200 Keplerian dynamical times (at 1.0kpc) in our simulations. We further find that the systems are stable once they reach the equilibrium state.