APOGEE chemical abundances of stars in the MW satellites Fornax, Sextans, Draco and Carina

TL;DR

This study uses APOGEE near-infrared spectra to analyze chemical abundances in stars from four MW satellite dwarf galaxies, revealing how galaxy mass influences chemical evolution and identifying potential remnants of destroyed globular clusters.

Contribution

First detailed chemical abundance analysis of stars in four MW satellite dwarf galaxies using APOGEE data, linking galaxy mass to chemical properties and identifying possible GC disruption relics.

Findings

Alpha element distribution correlates with galaxy luminosity and mass.

Dwarf galaxies show [Al/Fe] around -0.5, similar to metal-poor MW stars.

Nitrogen-rich stars in Fornax suggest relics of disrupted globular clusters.

Abstract

During its evolution, the Milky Way (MW) incorporated numerous dwarf galaxies, particularly low-mass systems. The surviving dwarf galaxies orbiting the MW serve as exceptional laboratories for studying the unique properties of these systems. Their metal-poor environments and shallow gravitational potentials likely drive significant differences in star formation and star cluster properties compared to those in the MW. Using high-quality near-infrared spectra from the APOGEE survey, we determined abundances of Fe, C, N, O, Mg, Al, Si, Ca, Ti, Cr, Mn, Ni, and Ce for 74 stars in four MW satellite dwarf galaxies: Fornax, Sextans, Draco, and Carina. Our analysis reveals that the distribution of $\alpha$ elements (e.g., [Si/Fe]) strongly correlates with galaxy luminosity (and hence mass), underscoring the critical role of galaxy mass in shaping chemical evolution. These dwarf galaxies exhibit [Al/Fe$]\sim -0.5$, which is comparable to those of the metal-poor stars in the MW. Additionally, we identified nitrogen-rich field stars in the Fornax dwarf galaxy, which display distinct metallicities compared to its known globular clusters (GCs). If these stars originated in GCs and subsequently escaped, their presence suggests we are observing relics of destroyed GCs, offering possible evidence of cluster disruption.