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arXiv · 2105.09155

Probing the hadronic nature of the gamma-ray emission associated with Westerlund 2

Enrique Mestre·Emma de Ona Wilhelmi·Diego F. Torres·Tim Lukas Holch·Ullrich Schwanke·Felix Aharonian·Pablo Saz Parkinson·Ruizhi Yang·Roberta Zanin
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Abstract

Star-forming regions have been proposed as potential Galactic cosmic-ray accelerators for decades. Cosmic-ray acceleration can be probed through observations of gamma-rays produced in inelastic proton-proton collisions, at GeV and TeV energies. In this paper, we analyze more than 11 years of Fermi-LAT data from the direction of Westerlund 2, one of the most massive and best-studied star-forming regions in our Galaxy. In particular, we investigate the characteristics of the bright pulsar PSR J1023-5746 that dominates the gamma-ray emission below a few GeV at the position of Westerlund 2, and the underlying extended source FGES J1023.3-5747. The analysis results in a clear identification of FGES J1023.3-5747 as the GeV counterpart of the TeV source HESS J1023-575, through its morphological and spectral properties. This identification provides new clues about the origin of the HESS J1023-575 gamma-ray emission, favouring a hadronic origin of the emission, powered by Westerlund 2, rather than a leptonic origin related to either the pulsar wind nebula associated with PSR J1023-5746 or the cluster itself. This result indirectly supports the hypothesis that star-forming regions can contribute to the cosmic-ray sea observed in our Galaxy

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Enrique Mestre, Emma de Ona Wilhelmi, Diego F. Torres, Tim Lukas Holch, Ullrich Schwanke, Felix Aharonian, Pablo Saz Parkinson, Ruizhi Yang, Roberta Zanin. 2021-05-19. Probing the hadronic nature of the gamma-ray emission associated with Westerlund 2. https://doi.org/10.1093/mnras/stab1455

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