Chemical Abundance Evidence of Enduring High Star Formation Rates in an Early Type Galaxy: High [Ca/Fe] in NGC 5128 Globular Clusters

TL;DR

This study analyzes globular clusters in NGC 5128 to reveal high calcium-to-iron ratios, indicating a rapid chemical enrichment history distinct from the Milky Way and M31.

Contribution

Introduces a novel high-resolution integrated light abundance analysis technique applied to NGC 5128 globular clusters, providing the first direct chemical history comparison with the Milky Way.

Findings

NGC 5128 clusters have higher [Ca/Fe] than MW and M31 clusters.

[Ca/Fe] in NGC 5128 suggests faster chemical enrichment.

Sample covers [Fe/H] from -1.6 to -0.2.

Abstract

We present [Fe/H], ages, and Ca abundances for an initial sample of 10 globular clusters in NGC 5128 obtained from high resolution, high signal-to-noise ratio echelle spectra of their integrated light. All abundances and ages are obtained using our original technique for high resolution integrated light abundance analysis of globular clusters. The clusters have a range in [Fe/H] between -1.6 to -0.2. In this sample, the average [Ca/Fe] for clusters with [Fe/H]<-0.4 is +0.37$\pm$0.07, while the average [Ca/Fe] in our MW and M31 GC samples is +0.29 $\pm$0.09 and +0.24 $\pm$0.10, respectively. This may imply a more rapid chemical enrichment history for NGC 5128 than for either the Milky Way or M31.This sample provides the first quantitative picture of the chemical history of NGC 5128 that is directly comparable to what is available for the Milky Way. Data presented here were obtained with the MIKE echelle spectrograph on the Magellan Clay Telescope.