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

Abstract

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