On The Metal-poor non-Sagittarius Globular Cluster NGC 5053: Orbit, Mg, Al, and Si

TL;DR

This study investigates the orbit and chemical abundances of the metal-poor globular cluster NGC 5053, revealing significant Al variation and Si enhancement, and challenges its proposed association with the Sagittarius dwarf galaxy.

Contribution

It provides new orbital analysis dismissing the Sgr connection and presents detailed near-infrared spectral measurements of Mg, Al, and Si in NGC 5053, highlighting complex chemical variations.

Findings

NGC 5053's orbit is inconsistent with Sgr association.

Large Al variation observed across stars.

Substantial Si enhancement detected.

Abstract

Metal-poor globular clusters (GCs) show intriguing Al-Mg and Si-Al correlations, which are important clues to decipher the multiple population phenomenon. NGC 5053 is one of the most metal-poor GCs, and has been suggested to be associated with the Sagittarius dwarf galaxy (Sgr), due to its similar location and radial velocity with one of the Sgr arms. In this work, we simulate the orbit of NGC 5053, and argue against the connection between Sgr and NGC 5053. Meanwhile, Mg, Al, and Si spectral lines, which are difficult to detect in the optical spectra, have been detected in the near-infrared APOGEE spectra. We use three different sets of stellar parameters and codes to derive the Mg, Al, and Si abundances, and we always see a large Al variation, and a substantial Si enhancement. Comparing with other metal-poor GCs, we suggest metallicity may not be the only parameter that controls the multiple populations.