APOGEE-2S view of the globular cluster Patchick 125 (Gran 3). New metallicity and elemental abundances from high-resolution spectroscopy

TL;DR

This study provides detailed elemental abundances, radial velocity, and orbital data for the metal-poor globular cluster Patchick 125, revealing its metallicity, chemical enrichment, and orbital characteristics, confirming its nature as a genuine globular cluster near the Galactic bulge.

Contribution

First high-resolution spectroscopic analysis of Patchick 125, establishing its metallicity, chemical abundances, and orbital parameters, confirming its status as a genuine globular cluster.

Findings

Metallicity range [Fe/H] = -1.69 to -1.72

Mean radial velocity of 95.9 km/s, higher than previous reports

Evidence of multiple populations with Al enrichment

Abstract

We present detailed elemental abundances, radial velocity, and orbital elements for Patchick~125, a recently discovered metal-poor globular cluster (GC) in the direction of the Galactic bulge. Near-infrared high-resolution ($R\sim22,500$) spectra of two members were obtained during the second phase of the Apache Point Observatory Galactic Evolution Experiment at Las Campanas Observatory as part of the sixteenth Data Release (DR 16) of the Sloan Digital Sky Survey. We investigated elemental abundances for four chemical species, including $\alpha$- (Mg, Si), Fe-peak (Fe), and odd-Z (Al) elements. We find a metallicity covering the range from [Fe/H] $= -1.69$ to $-1.72$, suggesting that Patchick~125 likely exhibits a mean metallicity $\langle$[Fe/H]$\rangle \sim -1.7$, which represents a significant increase in metallicity for this cluster compared to previous low-resolution spectroscopic analyses. We also found a mean radial velocity of 95.9 km s$^{-1}$, which is $\sim$21.6 km s$^{-1}$ higher than reported in the literature. The observed stars exhibit an $\alpha$-enrichment ([Mg/Fe]$\lesssim+0.20$, and [Si/Fe]$\lesssim +0.30$) that follows the typical trend of metal-poor GCs. The aluminum abundance ratios for the present two member stars are enhanced in [Al/Fe]$\gtrsim +0.58$, which is a typical enrichment characteristic of the so-called `second-generation' of stars in GCs at similar metallicity. This supports the possible presence of the multiple-population phenomenon in Patchick~125, as well as its genuine GC nature. Further, Patchick~125 shows a low-energy, low-eccentric ($<0.4$) and retrograde orbit captured by the inner Galaxy, near the edge of the bulge. We confirm that Patchick~125 is a genuine metal-poor GC, which is currently trapped in the vicinity of the Milky Way bulge.