Paper detail

The impact of galaxy geometry and mass evolution on the survival of star clusters

Direct N-body simulations of globular clusters in a realistic Milky Way-like potential are carried out using the code NBODY6 to determine the impact of the host galaxy disk mass and geometry on the survival of star clusters. A relationship between disk mass and star cluster dissolution timescale is derived. These N-body models show that doubling the mass of the disk from 5x10^10 solar masses to 10x10^10 solar masses halves the dissolution time of a satellite star cluster orbiting the host galaxy at 6 kpc from the galactic center. Different geometries in a disk of identical mass can determine either the survival or dissolution of a star cluster orbiting within the inner 6 kpc of the galactic center. Furthermore, disk geometry has measurable effects on the mass loss of star clusters up to 15 kpc from the galactic center. N-body simulations performed with a fine output time step show that at each disk crossing the outer layers of star clusters experience an increase in velocity dispersion of ~5% of the average velocity dispersion in the outer section of star clusters. This leads to an enhancement of mass-loss -- a clearly discernable effect of disk shocking. By running models with different inclinations we determine that star clusters with an orbit perpendicular to the Galactic plane have larger mass loss rates than both clusters evolving in the Galactic plane or in an inclined orbit.