On the role of Type Ia supernovae in the second generation star formation in globular clusters

TL;DR

This study uses 3D hydrodynamic simulations to explore how Type Ia supernovae influence second-generation star formation and chemical diversity in globular clusters, highlighting the importance of supernova timing and environmental density.

Contribution

It demonstrates the impact of SNe Ia on star formation and chemical properties in GCs, considering different delay times and gas densities, which was previously not well understood.

Findings

SN explosions can halt early SG star formation in low-density environments.

Delayed SN explosions allow for extended SG star formation with modest helium enrichment.

SNe Ia can produce an iron spread consistent with observations in some Galactic GCs.

Abstract

By means of 3D hydrodynamic simulations, we study how Type Ia supernovae (SNe) explosions affect the star formation history and the chemical properties of second generation (SG) stars in globular clusters (GC). SG stars are assumed to form once first generation asymptotic giant branch (AGB) stars start releasing their ejecta; during this phase, external gas is accreted by the system and SNe Ia begin exploding, carving hot and tenuous bubbles. Given the large uncertainty on SNe Ia explosion times, we test two different values for the 'delay time'. We run two different models for the external gas density: in the low-density scenario with short delay time, the explosions start at the beginning of the SG star formation, halting it in its earliest phases. The external gas hardly penetrates the system, therefore most SG stars present extreme helium abundances (Y > 0.33). The low-density model with delayed SN explosions has a more extended SG star formation epoch and includes SG stars with modest helium enrichment. On the contrary, the high-density model is weakly affected by SN explosions, with a final SG mass similar to the one obtained without SNe Ia. Most of the stars form from a mix of AGB ejecta and pristine gas and have a modest helium enrichment. We show that gas from SNe Ia may produce an iron spread of $\sim 0.14$ dex, consistent with the spread found in about 20% of Galactic GCs, suggesting that SNe Ia might have played a key role in the formation of this sub-sample of GCs.