Issue |
A&A
Volume 690, October 2024
|
|
---|---|---|
Article Number | A269 | |
Number of page(s) | 8 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/202450359 | |
Published online | 16 October 2024 |
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
1
The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, Sweden
2
Department of Astronomy, University of Texas at Austin, 2515 Speedway, Austin, Texas 78712, USA
3
Department of Astronomy, University of Maryland, College Park, MD 20742, USA
4
Observational Cosmology Lab, Code 665, NASA Goddard Space Flight Center, 8800 Greenbelt Rd., Greenbelt, MD 20771, USA
5
Center for Research and Exploration in Space Science and Technology, NASA/GSFC, Greenbelt, MD 20771, USA
6
Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
7
Department of Astronomy, University of Michigan, 1085 S. University Ave, Ann Arbor, MI 48109, USA
8
Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo, Norway
9
Department of Physics, University of Cincinnati, Cincinnati, OH 45221, USA
10
Department of Physics and Astronomy and PITT PACC, University of Pittsburgh, Pittsburgh, PA 15260, USA
11
Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
12
Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA
13
IPAC, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA
Received:
13
April
2024
Accepted:
5
August
2024
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 (Lyα) 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 Mdyn = (9 ± 1)×106 M⊙. Our age estimate of 4.2–4.5 Myr is much larger than the crossing time of tcross = 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 IIλ4686 and C IVλ5808 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.
Key words: stars: Wolf-Rayet / galaxies: evolution / galaxies: ISM / galaxies: starburst / galaxies: star clusters: general
Publisher note: The last name of first author is Rivera-Thorsen. It has been corrected on 1st November 2024.
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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