The Sunburst Arc with JWST: I. Detection of Wolf-Rayet stars injecting nitrogen into a low-metallicity, z = 2.37 proto-globular cluster leaking ionizing photons

We report the detection of a population of Wolf-Rayet (WR) stars in the Sunburst Arc, a strongly gravitationally lensed galaxy at redshift z = 2.37. As the brightest known lensed galaxy, the Sunburst Arc has become an important cosmic laboratory for studying star and cluster formation, Lyman α (Ly α...

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Veröffentlicht in:Astronomy and astrophysics (Berlin) 2024-10, Vol.690, p.A269
Hauptverfasser: Rivera-Thorsen, T. Emil, Chisholm, J., Welch, B., Rigby, J. R., Hutchison, T., Florian, M., Sharon, K., Choe, S., Dahle, H., Bayliss, M. B., Khullar, G., Gladders, M., Hayes, M., Adamo, A., Owens, M. R., Kim, K.
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Sprache:eng ; nor
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Zusammenfassung:We report the detection of a population of Wolf-Rayet (WR) stars in the Sunburst Arc, a strongly gravitationally lensed galaxy at redshift z = 2.37. As the brightest known lensed galaxy, the Sunburst Arc has become an important cosmic laboratory for studying star and cluster formation, Lyman α (Ly α ) radiative transfer, and Lyman continuum (LyC) escape. Here, we present the first results of JWST/NIRSpec IFU observations of the Sunburst Arc, focusing on a stacked spectrum of the 12-fold imaged Sunburst LyC-emitting (LCE) cluster. In agreement with previous studies, we find that the Sunburst LCE cluster is a very massive, compact star cluster with M dyn = (9 ± 1)×10 6 M ⊙ . Our age estimate of 4.2–4.5 Myr is much larger than the crossing time of t cross = 183 ± 9 kyr, indicating that the cluster is dynamically evolved and consistent with it being gravitationally bound. We find a significant nitrogen enhancement of the low ionization state interstellar medium (ISM), with log(N/O) = − 0.74 ± 0.09, which is ≈0.8 dex above typical values for H  II regions of a similar metallicity in the local Universe. We find broad stellar emission complexes around He  II λ 4686 and C  IV λ 5808 with associated nitrogen emission; this is the first time WR signatures have been directly observed at redshifts above ∼0.5. The strength of the WR signatures cannot be reproduced by stellar population models that only include single-star evolution. While models with binary evolution better match the WR features, they still struggle to reproduce the nitrogen-enhanced WR features. JWST reveals the Sunburst LCE cluster to be a highly ionized proto-globular cluster with low oxygen abundance and extreme nitrogen enhancement that hosts a population of WR stars, likely including a previously suggested population of very massive stars (VMSs), which together are rapidly enriching the surrounding medium.
ISSN:0004-6361
1432-0746
DOI:10.1051/0004-6361/202450359