A new formation model for omega Centauri: the crossroad of astrophysical processes

TL;DR

This study models omega Centauri's formation using hydrodynamical simulations that incorporate chemical enrichment processes, successfully explaining multiple stellar populations and their chemical properties within a dwarf galaxy context.

Contribution

It introduces a novel formation model for omega Centauri that includes detailed chemical enrichment and retention processes, aligning with observed stellar population features.

Findings

Multiple populations formed from a massive molecular cloud within a dwarf galaxy.

He-rich stars are centrally concentrated, creating a steep gradient.

Distinct chemical abundance patterns explained by retention of ejecta.

Abstract

We investigate the formation processes of the Galactic globular cluster (GC) omega Cen with multiple stellar populations based on our original hydrodynamical simulations with chemical enrichment by Type II supernovae (SNe II), asymptotic giant branch (AGB) stars, and neutron star mergers (NSMs). The principal results are as follows. Multiple stellar populations with a wide range of [Fe/H] can be formed from rather massive and compact molecular cloud with a mass of 2 * 10^7 M_sun in the central region of its dwarf galaxy within less than a few hundred Myr. Gas ejected from SNe II and AGB stars can mix well to form new stars with higher He abundances (Y) and higher [Fe/H]. The He-rich stars are strongly concentrated in the GC's central region so that the GC can show a steep negative gradient of Y. Relative ratios of light elements to Fe show bimodal distributions for a given [Fe/H] owing to star formation from original gas and AGB ejecta. [La/Fe] and [Ba/Fe] can rapidly increase until [Fe/H]~-1.5 and then decrease owing to Fe ejection from SNe II. Although AGB ejecta can be almost fully retained in intra-cluster medium, NSM ejecta can be retained only partially. This difference in the retention capability is responsible for the observed unique [Eu/Fe]-[Fe/H] and [La/Eu]-[Fe/H] relations in omega Cen. Some observational results such as the [O/Na]$-$[Fe/H] relation and radial [Fe/H] gradient are yet to be well reproduced in the present model.