Mergers of multi-metallic globular clusters: The role of dynamics
  Hubble Space Telescope observations of globular clusters (GCs) in the
Antennae galaxy show clusters of clusters, or regions in the galaxy that span
hundreds of parsecs, where many of the GCs are doomed to collide, and
eventually merge. Several such objects appear likely to present a significant
range in ages, hence possibly metallicities, and their merger could plausibly
lead to multi-metallic GCs. Here we explore this process with direct-summation
N-body simulations with GPU hardware. Our results reveal that colliding GCs
with different metallicities and ages can produce a GC with multiplicity and
occupation fractions not unlike those observed in multi-metallic clusters. In
our simulations, the merged clusters have a phase with a larger amount of
flattening than average, as a consequence of rapid rotation- thus suggesting
that relatively recent mergers may play a role in producing highly flattened,
multi-metallic clusters. We additionally explore the role of the King parameter
of the cluster in the occupation fractions with a set of 160 direct-summation
simulations and find that for equal size clusters the King parameter of the
progenitor clusters determines the occupation fractions in the merger product,
while in unequal size mergers the size of the clusters dominates the
distribution of stars in the new GC. In particular, we find that the observed
distribution of populations in Omega Cen can be described to some extent with
our dynamical models.
