Origin of Galactic Sub-PeV Diffuse Gamma-Ray Emission: Constraints from High-energy Neutrino Observations

Very recently, diffuse gamma-rays with 0.1 PeV < E γ < 1 PeV have been discovered from the Galactic disk by the Tibet air shower array and muon detector array (Tibet AS+MD array). While the measured sub-PeV flux may be compatible with the hadronic origin in the conventional Galactic cosmic-ray...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2021-06, Vol.914 (1), p.L7
Main Authors: Liu, Ruo-Yu, Wang, Xiang-Yu
Format: Article
Language:English
Subjects:
Arrays
Cosmic ray propagation
Cosmic ray showers
Diffuse radiation
Galactic cosmic rays
Galactic disk
Gamma emission
Gamma rays
Gamma-ray sources
High energy astronomy
Neutrinos
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Summary:Very recently, diffuse gamma-rays with 0.1 PeV < E γ < 1 PeV have been discovered from the Galactic disk by the Tibet air shower array and muon detector array (Tibet AS+MD array). While the measured sub-PeV flux may be compatible with the hadronic origin in the conventional Galactic cosmic-ray propagation model, we find that it is in possible tension with the nondetection of Galactic neutrino emissions by the IceCube neutrino telescope. We further find that the presence of an extra cosmic-ray component of relatively hard spectrum, which is probably related to the Cygnus Cocoon region and other PeV cosmic-ray sources in the Galactic disk, would alleviate the tension. This scenario implies the existence of an extreme accelerator of either protons or electrons beyond PeV in the Cygnus region, and predicts the continuation of the gamma-ray spectrum of Cygnus Cocoon up to 1 PeV with a possible hardening beyond ∼30–100 TeV.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8213/ac02c5