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

We investigate the dynamical evolution of compact young star clusters (CYCs)near the Galactic center (GC) using Aarseth's Nbody6 codes. The relativelysmall number of stars in the cluster (5,000-20,000) makes real-number N-bodysimulations for these clusters feasible on current workstations. UsingFokker-Planck (F-P) models, Kim, Morris, & Lee (1999) have made a survey ofcluster lifetimes for various initial conditions, and have found that clusterswith a mass <~ 2x10^4 Msun 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 thedynamical evolution, might violate assumptions made in F-P models. Here we findthat, 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 ofprojected number density profiles and stellar mass functions between N-bodysimulations and HST/NICMOS observations by Figer et al. (1999) suggests thatthe current tidal radius of the Arches cluster is ~1.0 pc, and the followingparameters for the initial conditions of that cluster: total mass of 2x10^4Msun and mass function slope for intermediate-to-massive stars of 1.75 (theSalpeter 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 notsignificantly affect the dynamical evolution of CYCs.Comment: 20 pages including 6 figures, To appear in ApJ, Dec 20 issu