Diffuse γ-ray emission from self-confined cosmic rays around Galactic sources

Abstract

The propagation of particles accelerated at supernova remnant shocks and escaping the parent remnants is likely to proceed in a strongly non-linear regime, due to the efficient self-generation of Alfvén waves excited through streaming instability near the sources. Depending on the amount of neutral hydrogen present in the regions around the sites of supernova explosions, cosmic rays may accumulate an appreciable grammage in the same regions and get self-confined for non-negligible times, which in turn results in an enhanced rate of production of secondaries. Here we calculate the contribution to the diffuse gamma-ray background due to the overlap along lines of sight of several of these extended halos as due to pion production induced by self-confined cosmic rays. We find that if the density of neutrals is low, the halos can account for a substantial fraction of the diffuse emission observed by Fermi-LAT, depending on the orientation of the line of sight with respect to the direction of the Galactic centre.

12 pages, 8 figures. Accepted for publication by MNRAS

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• High-energy particles and radiation in star-forming regions
• Diffusion of cosmic rays in MHD turbulence with magnetic mirrors
• Exploring particle escape in supernova remnants through gamma rays
• Self-Generated Cosmic-Ray Turbulence Can Explain the Morphology of TeV Halos
• Gamma rays as probes of cosmic-ray propagation and interactions in galaxies
• Measuring the Local Diffusion Coefficient with H.E.S.S. Observations of Very High-Energy Electrons
• Effects of reacceleration and source grammage on secondary cosmic rays spectra
• Evidence for Cosmic-Ray Escape in the Small Magellanic Cloud using Fermi Gamma-rays
• Interpretation of the excess of antiparticles within a modified paradigm of galactic cosmic rays
• Using Interstellar Clouds to Search for Galactic PeVatrons: Gamma-ray Signatures from Supernova Remnants
• Millisecond Pulsars Modify the Radio-SFR Correlation in Quiescent Galaxies
• Sensitivity of the Cherenkov Telescope Array to TeV photon emission from the Large Magellanic Cloud
• Escape of High Energy Particles from Bow-Shock Pulsar Wind Nebulae
• Nuclear de-excitation lines as a probe of low-energy cosmic rays
• Detection of gamma rays around SNR HB9 and its implication to the diffusive shock-acceleration history
• Cosmic-ray current-driven instabilities -- revisiting environmental conditions
• Regions of suppressed diffusion around supernova remnants?
• PeVatron Candidate SNR G106.3+2.7 in a Low-density Cavity: a Multiwavelength Test
• Self-confinement of low-energy cosmic rays around supernova remnants
• Hadronic Scenario for Galactic PeVatron LHAASO J1912+1014u Supported by Fermi-LAT $\gamma$-ray Data and FUGIN CO Data
• The self-control of Cosmic Rays