High energy cosmic rays and gamma rays from star clusters: the case of Cygnus OB2

Abstract

We investigate the acceleration of cosmic rays at the termination shock that results from the interaction of the collective wind of star clusters with the surrounding interstellar medium. The solution of the transport equation of accelerated particles in the wind-excavated cavity, including energy losses due to CR interactions with neutral gas in the bubble, shows several interesting properties that are discussed in detail. The issue of the maximum energy of the accelerated particles is discussed with special care, because of its implications for the origin of Galactic cosmic rays. Gamma ray emission is produced in the cavity due to inelastic pp scattering, while accelerated particles are advected downstream of the termination shock and diffuse at the same time. Both the spectrum and the morphology of such emission are discussed, with a comparison of our results with the observations of gamma ray emission from the Cygnus OB2 region.

Accepted for publication in MNRAS

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Cited by in corpus (6)

• The Origin of the Very-High-Energy Diffuse $\gamma$-Ray Emission: The Case for Galactic Source Cocoons
• Detection of molecular clouds in the PeVatron candidate source LHAASO J0341$+$5258 by the Nobeyama 45-m radio telescope
• Supernova remnants in super bubbles as cosmic ray accelerators
• On the hadronic origin of the very high energy $\gamma$-ray emission surrounding the young massive stellar cluster Westerlund 1
• Suppressed diffusion and gamma-ray emission from the Cygnus bubble
• Young Massive Star Clusters as TeV Emitters: Constraints from H.E.S.S. and LHAASO