Ionising Feedback Effects on Star Formation in Globular Clusters with Multiple Stellar Populations

TL;DR

This study uses 3D radiation-hydrodynamical simulations to investigate how ionising radiation influences second-generation star formation in massive, young globular clusters, finding it delays but does not prevent star formation.

Contribution

It provides new insights into the role of photoionisation feedback in the formation of multiple stellar populations within globular clusters, highlighting its delaying effect and impact on second-generation star mass.

Findings

Photoionisation heats but does not expel gas from the cluster.

Second-generation star formation is delayed by about 10 million years.

Photoionisation modestly reduces the total mass of second-generation stars.

Abstract

Using 3D radiation-hydrodynamical simulations, we study the effects of ionising radiation on the formation of second-generation (SG) stars in Globular Clusters (GCs) with multiple stellar populations. In particular, we focus on massive ($10^7 \mathrm{M}_{\odot}$) and young (40-Myr old) GCs. We consider stellar winds from asymptotic giant branch (AGB) stars, ram pressure, gas accretion onto the cluster, and photoionisation feedback of binary stars. We find that the stellar luminosity is strong enough to warm and ionise the intracluster medium, but it does not lead to a significant gas expulsion. The cluster can thus retain the ejecta of AGB stars and the accreted pristine gas. In addition, efficient cooling occurs in the central region of the cluster within $50 \mathrm{Myr}$ from the formation of first generation stars, leading to the formation of SG stars. Our results indicate that the inclusion of photoionisation does not suppress SG formation, but rather delays it by about $\sim10 \mathrm{Myr}$. The time delay depends on the density of the pristine gas, so that a denser medium exhibits a shorter delay in star formation. Moreover, photoionisation leads to a modest decrease in the total SG mass, compared to a model without it.