On the origin of the helium-rich population in Omega Centauri

TL;DR

This paper proposes a chemical evolution model suggesting that helium enrichment in Omega Centauri's blue main sequence stars results from selective metal loss via galactic winds, with helium retained through stellar winds.

Contribution

It introduces a model explaining helium enrichment through galactic outflows that preferentially remove metals, aligning with observed properties of Omega Centauri.

Findings

Galactic-scale outflows in a massive progenitor system explain helium enrichment.

Selective metal loss via winds accounts for observed abundance patterns.

Helium is retained through stellar winds, leading to helium-rich populations.

Abstract

To study the possible origin of the huge helium enrichment attributed to the stars on the blue main sequence of Omega Centauri, we make use of a chemical evolution model that has proven able to reproduce other major observed properties of the cluster, namely, its stellar metallicity distribution function, age-metallicity relation and trends of several abundance ratios with metallicity. In this framework, the key condition to satisfy all the available observational constraints is that a galactic-scale outflow develops in a much more massive parent system, as a consequence of multiple supernova explosions in a shallow potential well. This galactic wind must carry out preferentially the metals produced by explosive nucleosynthesis in supernovae, whereas elements restored to the interstellar medium through low-energy stellar winds by both asymptotic giant branch (AGB) stars and massive stars must be mostly retained. Assuming that helium is ejected through slow winds by both AGB stars and fast rotating massive stars (FRMSs), the interstellar medium of Omega Centauri's parent galaxy gets naturally enriched in helium in the course of its evolution.