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Arxiv: The Sunburst Arc with JWST: III. An Abundance of Direct Chemical Abundances Published: 5/10/2024 8:48:16 PM Updated: 2/12/2025 12:02:56 AM

Paper abstract: We measure the gas-phase abundances of the elements He, N, O, Ne, S, Ar, andFe in an individual H\textsc{ii} region known to be leaking Lyman-continuumphotons in the Sunburst Arc, a highly magnified galaxy at redshift z=2.37. Wedetect the temperature-sensitive auroral lines [SII]\lambda\lambda4069,4076,[OII]\lambda\lambda7320,7330, [SIII]\lambda6312, [OIII]\lambda4363, and[NeIII]\lambda3343 in a stacked spectrum of 5 multiple images of theLyman-continuum emitter (LCE), from which we directly measure the electrontemperature in the low, intermediate, and high ionization zones. We also detectthe density-sensitive doublets of [OII]\lambda\lambda3727,3729,[SII]\lambda\lambda6717,6731, and [ArIV]\lambda\lambda4713,4741, whichconstrain the density in both the low- and high-ionization gas. With thesetemperature and density measurements, we measure gas-phase abundances withsimilar rigor as studies of local galaxies. We measure a gas-phase metallicityfor the LCE of 12+\log(\textrm{O}/\textrm{H}) = 7.97 \pm 0.05, and find anenhanced nitrogen abundance \log(\textrm{N}/\textrm{O}) =-0.65^{+0.16}_{-0.25}. This nitrogen abundance is consistent with enrichmentfrom a population of Wolf-Rayet stars, additional signatures of which arereported in a companion paper. Abundances of sulfur, argon, neon, and iron areconsistent with local low-metallicity H\textsc{ii} regions and low-redshiftgalaxies. This study represents the most complete chemical abundance analysisof an individual H\textsc{ii} region at Cosmic Noon to date, which enablesdirect comparisons between local H\textsc{ii} regions and those in the distantuniverse.