Sulfur isotope ratios in the Large Magellanic Cloud

TL;DR

This study measures sulfur isotope ratios in the Large Magellanic Cloud, revealing lower ratios than the Milky Way, which provides insights into its chemical evolution and stellar nucleosynthesis in a metal-poor galaxy.

Contribution

First robust detection of C$^{33}$S in the LMC and precise measurement of sulfur isotope ratios, establishing benchmarks for extragalactic environments.

Findings

$^{34}$S/$^{33}$S ratio in LMC is about half of the Milky Way's

Low isotope ratios are linked to the LMC's low metallicity and star formation history

Detection of C$^{33}$S transitions on a 5 pc scale in the LMC

Abstract

Sulfur isotope ratios have emerged as a promising tool for tracing stellar nucleosynthesis, quantifying stellar populations, and investigating the chemical evolution of galaxies. While extensively studied in the Milky Way, in extragalactic environments they remain largely unexplored. 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. 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. We present the first robust detection of C$^{33}$S in the LMC by successfully identifying two C$^{33}$S transitions on a large scale of $\sim$5 pc. Our measurements result in an accurate determination of the $^{34}$S/$^{33}$S isotope ratio, which is 2.0$\pm$0.2. Our comparative analysis indicates that the $^{32}$S/$^{33}$S and $^{34}$S/$^{33}$S isotope ratios are about a factor of 2 lower in the LMC than in the Milky Way. Our findings suggest that the low $^{34}$S/$^{33}$S isotope ratio in the LMC can be attributed to a combination of the age effect, low metallicity, and star formation history.