Chemical abundances in the globular clusters NGC 5024 and NGC 5466 from optical and infrared spectroscopy

TL;DR

This study presents detailed chemical abundance measurements for five stars in two globular clusters, NGC 5466 and NGC 5024, using optical and infrared spectroscopy, revealing their metallicities and elemental patterns.

Contribution

It provides the first combined optical and infrared high-resolution chemical abundance analysis for these clusters, highlighting consistency and differences in elemental ratios.

Findings

NGC 5466 has [Fe/H] = -1.97 +/- 0.13 dex.

NGC 5024 has [Fe/H] = -2.06 +/- 0.13 dex.

Infrared-derived oxygen and silicon abundances are more consistent with other alpha-elements.

Abstract

Detailed chemical abundances for five stars in two Galactic globular clusters, NGC 5466 and NGC 5024, are presented from high resolution optical (from the Hobby- Eberley Telescope) and infrared spectra (from the SDSS-III APOGEE survey). We find [Fe/H] = -1.97 +/- 0.13 dex for NGC 5466, and [Fe/H] = -2.06 +/- 0.13 dex for NGC 5024, and the typical abundance pattern for globular clusters for the remaining elements, e.g., both show evidence for mixing in their light element abundance ratios (C, N), and AGB contributions in their heavy element abundances (Y, Ba, and Eu). These clusters were selected to examine chemical trends that may correlate them with the Sgr dwarf galaxy remnant, but at these low metallicities no obvious differences from the Galactic abundance pattern are found. Regardless, we compare our results from the optical and infrared analyses to find that oxygen and silicon abundances determined from the infrared spectral lines are in better agreement with the other alpha-element ratios and with smaller random errors.