Chemical Abundances in NGC 5053: A Very Metal-Poor and Dynamically Complex Globular Cluster

TL;DR

This study analyzes the chemical composition of NGC 5053, a very metal-poor and dynamically complex globular cluster, revealing its chemical similarity to Milky Way halo stars and its potential association with the Sagittarius stream.

Contribution

It provides detailed chemical abundance measurements of NGC 5053, highlighting its metal-poor nature and complex dynamical history, and discusses its possible origin in the Sagittarius stream.

Findings

NGC 5053 has an average [Fe/H] of -2.45, making it one of the most metal-poor GCs.

The cluster shows alpha-enhanced ratios and a Na-O anti-correlation similar to other GCs.

Chemical abundances are consistent with Milky Way halo stars at similar metallicity.

Abstract

NGC 5053 provides a rich environment to test our understanding of the complex evolution of globular clusters (GCs). Recent studies have found that this cluster has interesting morphological features beyond the typical spherical distribution of GCs, suggesting that external tidal effects have played an important role in its evolution and current properties. Additionally, simulations have shown that NGC 5053 could be a likely candidate to belong to the Sagittarius dwarf galaxy (Sgr dSph) stream. Using the Wisconsin-Indiana-Yale-NOAO-Hydra multi-object spectrograph, we have collected high quality (signal-to-noise ratio $\sim$ 75-90), medium-resolution spectra for red giant branch stars in NGC 5053. Using these spectra we have measured the Fe, Ca, Ti, Ni, Ba, Na, and O abundances in the cluster. We measure an average cluster [Fe/H] abundance of -2.45 with a standard deviation of 0.04 dex, making NGC 5053 one of the most metal-poor GCs in the Milky Way (MW). The [Ca/Fe], [Ti/Fe], and [Ba/Fe] we measure are consistent with the abundances of MW halo stars at a similar metallicity, with alpha-enhanced ratios and slightly depleted [Ba/Fe]. The Na and O abundances show the Na-O anti-correlation found in most GCs. From our abundance analysis it appears that NGC 5053 is at least chemically similar to other GCs found in the MW. This does not, however, rule out NGC 5053 being associated with the Sgr dSph stream.