Sulfur isotope ratios in the Large Magellanic Cloud

Abstract

Context. Sulfur isotope ratios have emerged as a promising tool for tracing stellar nucleosynthesis, quantifying stellar populations, and investigating the chemical evolution of galaxies. While they are extensively studied in the context of the Milky Way, they still remain largely unexplored in extragalactic environments. Aims. We focus on investigating the sulfur isotope ratios in the Large Magellanic Cloud (LMC) to gain insights into sulfur enrichment in this nearby system and to establish benchmarks for such ratios in metal-poor galaxies. Methods. We conducted pointed observations of CS and its isotopologues toward N113, one of the most prominent star-formation regions in the LMC, utilizing the Atacama Pathfinder EXperiment 12 m telescope. Results. We present the first robust detection of C33S in the LMC by successfully identifying two C33S transitions on a large scale of ∼5 pc. Our measurements result in an accurate determination of the 34S/33S isotope ratio, which is 2.0 ± 0.2. Our comparative analysis indicates that the 32S/33S and 34S/33S isotope ratios are about a factor of two lower in the LMC than in the Milky Way. Conclusions. Our findings suggest that the low 34S/33S isotope ratio in the LMC can be attributed to a combination of the age effect, low metallicity, and star formation history.