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Arxiv: The Sunburst Arc with JWST: Detection of Wolf-Rayet stars injecting nitrogen into a low-metallicity, z=2.37 proto-globular cluster leaking ionizing photons Published: 4/13/2024 6:10:18 AM Updated: 4/13/2024 6:10:18 AM

Paper abstract: We report the detection of a population of Wolf-Rayet (WR) stars in theSunburst Arc, a strongly gravitationally lensed galaxy at redshift z=2.37. Asthe brightest known lensed galaxy, the Sunburst Arc has become an importantcosmic laboratory for studying star and cluster formation, Lyman \alpharadiative transfer, and Lyman Continuum (LyC) escape. Here, we present thefirst results of JWST/NIRCam imaging and NIRSpec IFU observations of theSunburst Arc, focusing on a stacked spectrum of the 12-fold imaged LyC-emitting(Sunburst LCE) cluster. In agreement with previous studies, we find that thecluster is massive and compact, with M_{\text{dyn}} = (9\pm1) \times 10^{6}M_{\odot}, Our age estimate of 4.2--4.5 Myr is much larger than the crossingtime of t_{\text{cross}} = 183 \pm 9 kyr, indicating that the cluster isdynamically evolved and consistent with being gravitationally bound. We find asignificant nitrogen enhancement of the low ionization state ISM, with\log(N/O) = -0.74 \pm 0.09, which is ~ 0.8 dex above typical valuesfor H II regions of similar metallicity in the local Universe. We find broadstellar emission complexes around He II\lambda 4686 and C IV\lambda 5808with associated nitrogen emission -- this is the first time WR signatures havebeen directly observed at redshifts above ~ 0.5. The strength of the WRsignatures cannot be reproduced by stellar population models that only includesingle-star evolution. While models with binary evolution better match the WRfeatures, they still struggle to reproduce the nitrogen-enhanced WR features.JWST reveals the Sunburst LCE to be a highly ionized, proto-globular clusterwith low oxygen abundance and extreme nitrogen enhancement that hosts apopulation of Wolf-Rayet stars, and possibly Very Massive stars (VMSs), whichare rapidly enriching the surrounding medium.