Please use this identifier to cite or link to this item:
https://hdl.handle.net/2440/136915
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Type: | Journal article |
Title: | A deep spectromorphological study of the γ-ray emission surrounding the young massive stellar cluster Westerlund 1 |
Author: | Aharonian, F. Ashkar, H. Backes, M. Barbosa Martins, V. Becherini, Y. Berge, D. Bi, B. Böttcher, M. de Bony de Lavergne, M. Bradascio, F. Brose, R. Brun, F. Bulik, T. Burger-Scheidlin, C. Cangemi, F. Caroff, S. Casanova, S. Cerruti, M. Chand, T. Chandra, S. et al. |
Citation: | Astronomy and Astrophysics: a European journal, 2022; 666:1-18 |
Publisher: | EDP Sciences |
Issue Date: | 2022 |
ISSN: | 0004-6361 1432-0746 |
Statement of Responsibility: | H.E.S.S Collaboration ... F. Aharonian ... G. Rowell ... A. Mitchell ... J. Muller ... M. Sasaki ... et al. |
Abstract: | Context: Young massive stellar clusters are extreme environments and potentially provide the means for efficient particle acceleration. Indeed, they are increasingly considered as being responsible for a significant fraction of cosmic rays (CRs) that are accelerated within the Milky Way. Westerlund 1, the most massive known young stellar cluster in our Galaxy, is a prime candidate for studying this hypothesis. While the very-highenergy γ-ray source HESS J1646−458 has been detected in the vicinity of Westerlund 1 in the past, its association could not be firmly identified. Aims: We aim to identify the physical processes responsible for the γ-ray emission around Westerlund 1 and thus to understand the role of massive stellar clusters in the acceleration of Galactic CRs better. Methods: Using 164 h of data recorded with the High Energy Stereoscopic System (H.E.S.S.), we carried out a deep spectromorphological study of the γ-ray emission of HESS J1646−458. We furthermore employed H I and CO observations of the region to infer the presence of gas that could serve as target material for interactions of accelerated CRs. Results: We detected large-scale (∼2 ◦ diameter) γ-ray emission with a complex morphology, exhibiting a shell-like structure and showing no significant variation with γ-ray energy. The combined energy spectrum of the emission extends to several tens of TeV, and it is uniform across the entire source region. We did not find a clear correlation of the γ-ray emission with gas clouds as identified through H I and CO observations. Conclusions: We conclude that, of the known objects within the region, only Westerlund 1 can explain the majority of the γ-ray emission. Several CR acceleration sites and mechanisms are conceivable and discussed in detail. While it seems clear that Westerlund 1 acts as a powerful particle accelerator, no firm conclusions on the contribution of massive stellar clusters to the flux of Galactic CRs in general can be drawn at this point. |
Keywords: | acceleration of particles; radiation mechanisms; non-thermal; shock waves; stars; massive; gamma rays; galaxies; star clusters; Westerlund 1 |
Rights: | © F. Aharonian et al. 2022. 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. This article is published in open access under the Subscribe-to-Open model. Open access funding provided by Max Planck Society |
DOI: | 10.1051/0004-6361/202244323 |
Published version: | http://dx.doi.org/10.1051/0004-6361/202244323 |
Appears in Collections: | Physics publications |
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File | Description | Size | Format | |
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hdl_136915.pdf | Published version | 3.48 MB | Adobe PDF | View/Open |
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