The Dynamics of Multiple Populations in the Globular Cluster NGC 6362
Abstract
We investigate how the Milky Way tidal field can affect the spatial mixing of
multiple stellar populations in the globular cluster NGC 6362. We use $N$-body
simulations of multiple population clusters on the orbit of this cluster around
the Milky Way. Models of the formation of multiple populations in globular
clusters predict that the second population should initially be more centrally
concentrated than the first. However, NGC 6362 is comprised of two chemically
distinct stellar populations having the same radial distribution. We show that
the high mass loss rate experienced on this cluster's orbit significantly
accelerates the spatial mixing of the two populations expected from two body
relaxation. We also find that for a range of initial second population
concentrations, cluster masses, tidal filling factors and fraction of first
population stars, a cluster with two populations should be mixed when it has
lost 70-80 per cent of its initial mass. These results fully account for the
complete spatial mixing of NGC 6362, since, based on its shallow present day
mass function, independent studies estimate that the cluster has lost 85 per
cent of its initial mass.