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Arxiv: The JWST EXCELS survey: tracing the chemical enrichment pathways of high-redshift star-forming galaxies with O, Ar and Ne abundances Published: 11/18/2024 8:55:24 PM Updated: 11/18/2024 8:55:24 PM

Paper abstract: We present an analysis of nine star-forming galaxies with \langle z \rangle= 3.95 from the JWST EXCELS survey for which we obtain robust chemicalabundance estimates for the \alpha-elements O, Ne and Ar. The\alpha-elements are primarily produced via core-collapse supernovae (CCSNe)which should result in \alpha-element abundance ratios that do not varysignificantly across cosmic time. However, Type Ia supernovae (SNe Ia) modelspredict an excess production of Ar relative to O and Ne. The Ar/O abundanceratio can therefore be used as a tracer of the relative enrichment of CCSNe andSNe Ia in galaxies. Our sample approximately doubles the number of sources withmeasurements of {\rm Ar/O} at z > 2, and we find that our sample exhibitssub-solar Ar/O ratios on average, with \rm{Ar/O} = 0.62 \pm 0.10 \,(\rm{Ar/O})_{\odot}. In contrast, the average Ne/O abundance is fullyconsistent with the solar ratio, with \rm{Ne/O} = 1.07 \pm 0.12 \,(\rm{Ne/O})_{\odot}. Our results support a scenario in which Ar has not hadtime to build up in the interstellar medium of young high-redshift galaxies,which are dominated by CCSNe enrichment. We show that these abundance estimatesare in good agreement with recent Milky Way chemical evolution models, and withAr/O trends observed for planetary nebulae in the Andromeda galaxy. Theseresults highlight the potential for using multiple element abundance ratios toconstrain the chemical enrichment pathways of early galaxies with JWST.