Chemical Abundances of the Highly Obscured Galactic Globular Clusters 2MASS GC02 and Mercer 5

TL;DR

This study provides the first high-resolution infrared spectral analysis of two obscured Galactic globular clusters, revealing their chemical compositions and confirming their status as typical bulge clusters.

Contribution

First detailed chemical abundance analysis of Mercer 5 and 2MASS GC02 using high-resolution near-infrared spectroscopy, expanding knowledge of obscured bulge clusters.

Findings

Mercer 5 has [Fe/H] = -0.86; 2MASS GC02 has [Fe/H] = -1.08.

Mercer 5 shows enhanced alpha-element ratios, consistent with bulge stars.

Both clusters are confirmed as typical bulge globular clusters.

Abstract

We present the first high spectral resolution abundance analysis of two newly discovered Galactic globular clusters, namely Mercer 5 and 2MASS GC02 residing in regions of high interstellar reddening in the direction of the Galactic center. The data were acquired with the Phoenix high-resolution near-infrared echelle spectrograph at Gemini South (R~50000) in the 15500.0 A - 15575.0 A spectral region. Iron, Oxygen, Silicon, Titanium and Nickel abundances were derived for two red giant stars, in each cluster, by comparing the entire observed spectrum with a grid of synthetic spectra generated with MOOG. We found [Fe/H] values of -0.86 +/- 0.12 and -1.08 +/- 0.13 for Mercer 5 and 2MASS GC02 respectively. The [O/Fe], [Si/Fe] and [Ti/Fe] ratios of the measured stars of Mercer 5 follow the general trend of both bulge field and cluster stars at this metallicity, and are enhanced by > +0.3. The 2MASS GC02 stars have relatively lower ratios, but still compatible with other bulge clusters. Based on metallicity and abundance patterns of both objects we conclude that these are typical bulge globular clusters.