Spatial Mixing of Multiple Stellar Populations in Globular Clusters

We present here the results of a survey of N-body simulations aimed at exploring the long-term dynamical evolution of globular clusters with multiple stellar populations and the spatial mixing of first-generation (FG) and second-generation stars (SG). Our previous investigations on the formation and evolution of multiple population clusters suggested that SG stars formed from the ejecta of FG AGB stars are expected initially to be concentrated in the cluster inner regions. Our simulations show that until mixing is complete and the radial profile of the ratio of the number of SG/FG number ratio, NSG/NFG, is flat over the entire cluster, the radial profile of NSG/NFG is characterized by three regions: 1) a flat inner part; 2) a declining part in which FG stars are increasingly dominant; and 3) an outer region where the NSG /NFG profile flattens again (the NSG /NFG profile may rise slightly again in the outermost cluster regions). The distance from the cluster center at which the local value of NSG/NFG equals the global value of this number ratio is approximately between 1 and 2 cluster half-mass radii. We have studied the dependence of the mixing timescale on the SG initial concentration and our simulations suggest that in many Galactic globular clusters the SG should still be more spatially concentrated than the FG.