Description
Globular clusters serve as important tracers of their host galaxies' chemical evolution and star formation history. In this study, we present a comprehensive chemical abundance analysis of Sextans A GC-1, a globular cluster located in a low-surface-brightness dwarf irregular galaxy on the outskirts of the Local Group. Using integrated-light spectroscopy, we determine the cluster’s detailed chemical composition, including α-elements, iron-peak elements, and heavy elements, while also deriving its dynamical mass and mass-to-light ratio.
Our analysis reveals that GC-1 is younger and more metal-poor than typical Milky Way GCs, with a notably high dynamical mass and mass-to-light ratio. The abundance patterns indicate a complex chemical enrichment history, with α-elements exhibiting both depletion and enhancement, iron-peak elements largely at scaled-solar levels, and heavy elements showing distinct deviations from Milky Way star clusters’ trends. Particularly striking is the unusually low Mg abundance ([Mg/Fe]=−0.79 ± 0.29), a feature rarely observed in other globular clusters.
The elevated mass-to-light ratio suggests the possibility of a varying stellar initial mass function or the presence of an intermediate-mass black hole. Meanwhile, the Mg deficiency may indicate unique nucleosynthetic processes in the cluster’s formation environment. This star cluster occupies an unpopulated area in the Local Group on the age-metallicity plot with its uncommon combination of young and metal-poor nature. These findings highlight Sextans A GC-1 as an intriguing target for further studies, providing valuable insights into the formation and evolution of globular clusters in low-mass galaxies.
