N-Body Simulations of Compact Young Clusters near the Galactic Center

TLDR: In this paper, the authors investigated the dynamical evolution of compact young star clusters near the Galactic center using Aarseth's Nbody6 codes and found that, in most cases, the CYC lifetimes of previous Fokker-Planck (F-P) calculations are 5%-30% shorter than those from the present N-body simulations.

Abstract: We investigate the dynamical evolution of compact young star clusters (CYCs) near the Galactic center using Aarseth's Nbody6 codes. The relatively small number of stars in the cluster (5000-20,000) makes real-number N-body simulations for these clusters feasible on current workstations. Using Fokker-Planck (F-P) models, Kim, Morris, & Lee made a survey of cluster lifetimes for various initial conditions and have found that clusters with a mass 2 × 104 M☉ evaporate in ~10 Myr. These results were, however, to be confirmed by N-body simulations because some extreme cluster conditions, such as strong tidal forces and a large stellar mass range participating in the dynamical evolution, might violate assumptions made in F-P models. Here we find that, in most cases, the CYC lifetimes of previous F-P calculations are 5%-30% shorter than those from the present N-body simulations. The comparison of projected number density profiles and stellar mass functions between N-body simulations and Hubble Space Telescope/NICMOS observations by Figer and colleagues in 1999 suggests that the current tidal radius of the Arches cluster is ~1.0 pc and that the parameters for the initial conditions of that cluster are as follows: total mass of 2 × 104 M☉ and mass function slope for intermediate to massive stars of 1.75 (the Salpeter function has 2.35). We also find that the lower stellar mass limit, the presence of primordial binaries, the amount of initial mass segregation, and the choice of initial density profile (King or Plummer models) do not significantly affect the dynamical evolution of CYCs.