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

Abstract

We investigate the dynamical evolution of compact young star clusters (CYCs) near the Galactic center using AarsethÏs Nbody6 codes. The relatively small number of stars in the cluster (5000È20,000) 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 were, however, to be conÐrmed 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 Ðnd that, in most cases, the CYC lifetimes of previous F-P calculations are 5%È30% shorter than those from the present N-body simulations. The comparison of projected number density proÐles 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 D1.0 pc and that the parameters for the initial conditions of that cluster are as follows: total mass of 2]104 [2]104 M_ evaporate in D10 Myr. These results M_ and mass function slope for intermediate to massive stars of 1.75 (the Salpeter function has 2.35). We also Ðnd that the lower stellar mass limit, the presence of pri- mordial binaries, the amount of initial mass segregation, and the choice of initial density proÐle (King or Plummer models) do not signiÐcantly a†ect the dynamical evolution of CYCs.