On the Origin of Multiple Populations During Massive Star Cluster Formation

TL;DR

This study uses 3D radiative hydrodynamics simulations to explore how multiple stellar populations in globular clusters can naturally form during the early stages of massive star cluster formation through chemical self-enrichment.

Contribution

It demonstrates that multiple populations can arise rapidly during cluster formation via simple enrichment scenarios, supported by realistic simulation data.

Findings

Multiple populations can form within 5 Myr of cluster formation.

Helium enrichment of a few percent of cluster mass reproduces observed features.

Different enrichment histories lead to diverse population ratios.

Abstract

We investigate the possibility that multiple populations in globular clusters arise as a natural by-product of massive star-cluster formation. We use 3D radiative hydrodynamics simulations for the formation of young massive clusters to track their chemical self-enrichment during their first 5 Myr. These clusters form embedded within filamentary Giant Molecular Clouds by a combination of gas accretion and rapid merging of protoclusters. Chemical enrichment is a dynamic process happening as the young cluster assembles, so that the original (1P) and enriched (2P) subpopulations of stars form almost simultaneously. Here we test two simple and opposite extremes for the injection of enriched material into the intracluster gas: we assume either continuous injection in a way that tracks the star formation rate; or sudden injection by a single instantaneous event. Using helium abundance as a proxy for the enrichment, we find that realistic multiple population features can be reproduced by injecting a total helium mass amounting to a few percent of the cluster's total mass. The differences in individual growth histories can lead to widely differing 1P/2P outcomes. These models suggest that dual or multiple populations can emerge rapidly in massive star clusters undergoing the typical mode of star cluster formation.