Aharonian F, Ashkar H, Backes M, Martins VB, Becherini Y, Berge D, Bi B, Böttcher M, De Lavergne MDB, Bradascio F, Brose R, Brun F, Bulik T, Burger-Scheidlin C, Cangemi F, Caroff S, Casanova S, Cerruti M, Chand T, Chandra S, Chen A, Chibueze O, Cristofari P, Mbarubucyeye JD, Djannati-Ataï A, Ernenwein JP, Feijen K, De Clairfontaine GF, Fontaine G, Funk S, Gabici S, Gallant YA, Ghafourizadeh S, Giavitto G, Giunti L, Glawion D, Glicenstein JF, Goswami P, Grondin MH, Härer LK, Haupt M, Hinton JA, Hörbe M, Hofmann W, Holch TL, Holler M, Horns D, Jamrozy M, Joshi V, Jung-Richardt I, Kasai E, Katarzyński K, Katz U, Khélifi B, Kluźniak W, Komin N, Kosack K, Kostunin D, Mezek GK, Lang RG, Le Stum S, Lemière A, Lemoine-Goumard M, Lenain JP, Leuschner F, Lohse T, Luashvili A, Lypova I, Mackey J, Majumdar J, Malyshev D, Marandon V, Marchegiani P, Marcowith A, Martí-Devesa G, Marx R, Maurin G, Meyer M, Mitchell A, Moderski R, Mohrmann L, Montanari A, Moulin E, Muller J, Murach T, Nakashima K, De Naurois M, Nayerhoda A, Niemiec J, Ohm S, Olivera-Nieto L, Wilhelmi EDO, Ostrowski M, Panny S, Panter M, Parsons RD, Peron G, Prokhorov DA, Pühlhofer G, Punch M, Quirrenbach A, Rauth R, Reichherzer P, Reimer A, Reimer O, Renaud M, Reville B, Rieger F, Rowell G, Rudak B, Ruiz-Velasco E, Sahakian V, Salzmann H, Sanchez DA, Santangelo A, Sasaki M, Schüssler F, Schutte HM, Schwanke U, Shapopi JNS, Specovius A, Spencer S, Stawarz Ł, Steenkamp R, Steinmassl S, Steppa C, Sushch I, Suzuki H, Takahashi T, Tanaka T, Terrier R, Thorpe-Morgan C, Tsirou M, Tsuji N, Tuffs R, Unbehaun T, van Eldik C, Van Soelen B, Vecchi M, Veh J, Venter C, Vink J, Wagner SJ, White R, Wierzcholska A, Wong YW, Zacharias M, Zargaryan D, Zdziarski AA, Zhu SJ, Zouari S, Żywucka N, Blackwell R, Braiding C, Burton M, Cubuk K, Filipović M, Tothill N, Wong G (2022)
Publication Language: English
Publication Type: Journal article
Publication year: 2022
Book Volume: 666
Article Number: A124
DOI: 10.1051/0004-6361/202244323
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-high-energy 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.
APA:
Aharonian, F., Ashkar, H., Backes, M., Martins, V.B., Becherini, Y., Berge, D.,... Wong, G. (2022). A deep spectromorphological study of the γ -ray emission surrounding the young massive stellar cluster Westerlund 1. Astronomy & Astrophysics, 666. https://doi.org/10.1051/0004-6361/202244323
MLA:
Aharonian, F., et al. "A deep spectromorphological study of the γ -ray emission surrounding the young massive stellar cluster Westerlund 1." Astronomy & Astrophysics 666 (2022).
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