Probing Abundance Variations among Multiple Stellar Populations in the Metal-Poor Globular Cluster NGC 2298 using Gemini-South/GHOST

TL;DR

This study analyzes the chemical abundances of 13 stars in the metal-poor globular cluster NGC 2298 using Gemini-South/GHOST, revealing abundance variations and complex enrichment processes among multiple stellar populations.

Contribution

First detailed chemical abundance analysis of NGC 2298 with GHOST, identifying abundance variations and complex enrichment among multiple stellar generations.

Findings

Detected chemical anomalies among light elements, classifying stars into different generations.

Found significant dispersion in Sc, Ni, and Zn abundances between generations.

Observed correlations between neutron-capture element ratios and Mg, indicating complex nucleosynthesis.

Abstract

Studying the abundances in metal-poor globular clusters is crucial for understanding the formation of the Galaxy and the nucleosynthesis processes in the early Universe. We observed 13 red giant stars from the metal-poor globular cluster NGC 2298 using the newly commissioned GHOST spectrograph at Gemini South. We derived stellar parameters and abundances for 36 species across 32 elements, including 16 neutron-capture elements. We find that the stars exhibit chemical anomalies among the light elements, allowing us to classify them into first-generation (8 stars) and second-generation (5 stars). We derive a mean cluster metallicity of [Fe/H]=-1.98 +/- 0.10 with no significant variation among cluster members. Most alpha- and Fe-peak elements display low star-to-star abundance dispersion, with notable exceptions for Sc, Ni, and Zn for which the dispersions in Sc vary significantly between stars from different generations to 2\sigma levels. Similarly, among the neutron-capture elements, we observed considerable differences in dispersion for Sr and Eu among the first and second generation stars to 2 sigma levels. We also confirm an intrinsic scatter beyond observational uncertainties for several elements using a maximum likelihood approach among stars from different generations. Additionally, we note an increase in [Sr/Eu] and [Ba/Eu] with [Mg/Fe] in first-generation stars indicating correlations between the productions of light r-process and Mg. We find the universal r-process pattern, but with larger dispersions in the main r-process than the limited-r elements. These differences in abundance dispersion, among first- and second-generation stars in NGC 2298, suggest complex and inhomogeneous early chemical enrichment processes, driven by contributions from multiple nucleosynthetic events, including massive stars and rare r-process events.