APOGEE Chemical Abundances of Globular Cluster Giants in the Inner Galaxy

TL;DR

This study uses APOGEE data to analyze chemical abundances in globular cluster giants near the Galactic center, revealing multiple stellar populations and abundance variations that inform models of cluster self-enrichment.

Contribution

It provides new quantitative constraints on globular cluster self-enrichment models by analyzing chemical abundance spreads in inner Galaxy clusters.

Findings

Multiple populations detected in four clusters and evidence in a fifth.

Significant abundance spreads in N, C, Na, and Al observed.

Results support using N-rich field stars as tracers of globular cluster origins.

Abstract

We report chemical abundances obtained by SDSS-III/APOGEE for giant stars in five globular clusters located within 2.2 kpc of the Galactic centre. We detect the presence of multiple stellar populations in four of those clusters (NGC 6553, NGC 6528, Terzan 5, and Palomar 6) and find strong evidence for their presence in NGC 6522. All clusters present a significant spread in the abundances of N, C, Na, and Al, with the usual correlations and anti-correlations between various abundances seen in other globular clusters. Our results provide important quantitative constraints on theoretical models for self-enrichment of globular clusters, by testing their predictions for the dependence of yields of elements such as Na, N, C, and Al on metallicity. They also confirm that, under the assumption that field N-rich stars originate from globular cluster destruction, they can be used as tracers of their parental systems in the high- metallicity regime.