2021/05/31 by Sergey Koldobskiy, S. Koldobskiy, A. Neronov +3
Physics and Astronomy · #Astrophysics #Astrophysics and Cosmic Phenomena #Atomic physics #Cosmic ray #Dark Matter and Cosmic Phenomena #Fermi Gamma-ray Space Telescope #Gamma-ray bursts and supernovae #Nuclear physics #Physics #Pion #Quantum mechanics #Rigidity (electromagnetism) #astro-ph.HE
paper · pdf · doi:10.1103/physrevd.104.043010
published as Phys. Rev. D 104, 043010 (2021) · 5 pages, 2 figures
openalex created_date 2021/05/10 · openalex publication_date 2021/08/13 · arxiv created 2021/08/17 · arxiv updated 2021/08/18 · openalex updated_date 2026/08/05
The Tibet-AS\ensuremathγ Collaboration has recently reported a measurement of diffuse \ensuremathγ-ray flux from the outer Galactic disk in the energy range reaching PeV. We complement this measurement with the Fermi/LAT measurement of the diffuse flux from the same sky region and study the pion decay model of the combined Fermi/LAT+Tibet\text\ensuremath-AS\ensuremathγ spectrum. We find that within such a model the average cosmic-ray spectrum in the outer Galactic disk has the same characteristic features as the local cosmic-ray spectrum. In particular, it experiences a hardening at several hundred GV rigidity and a knee feature in the PV rigidity range. The slope of the average cosmic-ray spectrum above the break is close to the locally observed slope of the helium spectrum \ensuremathγ\ensuremath≃2.5, but is harder than the slope of the local proton spectrum in the same rigidity range. Although the combination of Fermi/LAT and Tibet-AS\ensuremathγ data points to the presence of the knee in the average cosmic-ray spectrum, the quality of the data is not yet sufficient for the study of knee shape and cosmic-ray composition.