The Origin and Chemical Evolution of the Exotic Globular Cluster NGC3201

TL;DR

This study provides a detailed chemical analysis of NGC3201, revealing its possible extragalactic origin through kinematic data and chemical signatures, while showing similarities to native Galactic globular clusters in chemical evolution.

Contribution

It offers the first detailed chemical abundance analysis of NGC3201's RGB stars, highlighting its peculiar kinematics and chemical patterns to infer its origin.

Findings

NGC3201 has a metallicity of [Fe/H] = -1.53 with possible small spread.

Presence of an extended Na-O anticorrelation.

Chemical evolution similar to native Galactic GCs despite extragalactic kinematics.

Abstract

NGC3201 is a globular cluster (GC) which shows very peculiar kinematic characteristics including an extreme radial velocity and a highly retrograde orbit, strongly suggesting an extraGalactic origin. Our aims are to study NGC3201 in the context of multiple populations (MPs), hoping to constrain possible candidates for the self-enrichment by studying the chemical abundance pattern, as well as adding insight into the origin of this intriguing cluster. We present a detailed chemical abundance analysis of eight red giant branch (RGB) stars using high resolution spectroscopy. We measured 29 elements and found [Fe/H]=-1.53+/-0.01, we cannot rule out a metallicity spread of ~0.12 dex, and an alpha-enhancement typical of halo GCs. However significant spreads are observed in the abundances of all light elements except for Mg. We confirm the presence of an extended Na-O anticorrelation. n-capture elements generally are dominated by the r-process, in good agreement with the bulk of Galactic GCs. The total (C+N+O) abundance is slightly supersolar and requires a small downward correction to the isochrone age, yielding 11.4 Gyr. Kinematically, NGC3201 appears likely to have had an extraGalactic origin but its chemical evolution is similar to most other, presumably native, Galactic GCs.