The Emergence of Multiple Populations in Radiation Hydrodynamics
  Simulations of Cluster Formation
  We present a new approach to understanding star-to-star helium abundance
variations within globular clusters. We begin with detailed radiation
hydrodynamics simulations of cluster formation within giant molecular clouds,
and investigate the conditions under which multiple populations could be
created. Chemical enrichment occurs dynamically as the cluster is assembled. We
test two extreme mechanisms for injection of enriched gas within the clusters,
and find that realistic multiple populations can be formed in both mechanisms.
The stochastic cluster formation histories are dictated by the inherent
randomness of the timing and location of the formation of small clusters, which
rapidly merge to build up the larger cluster, in combination with continual
accretion of gas from the cloud. These cluster formation histories naturally
produce a diversity of abundance patterns across the massive cluster
population. We conclude that multiple populations are a natural outcome of the
typical mode of star cluster formation.
