Pion decay model of the Tibet-ASγ PeV gamma-ray signal
|Author:||Koldobskiy, Sergey1,2; Neronov, Andrii3,4; Semikoz, Dmitri3,5,1|
1National Research Nuclear University MEPhI, 115409 Moscow, Russia
2University of Oulu, 90570 Oulu, Finland
3Université de Paris, CNRS, Astroparticule et Cosmologie, F-75006 Paris, France
4Astronomy Department, University of Geneva, Chemin d’Ecogia 16, 1290 Versoix, Switzerland
5Institute for Nuclear Research of the Russian Academy of Sciences, Moscow 117312, Russia
|Online Access:||PDF Full Text (PDF, 0.5 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe2021082544215
American Physical Society,
|Publish Date:|| 2021-08-25
The Tibet-ASγ Collaboration has recently reported a measurement of diffuse γ-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-ASγ 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 γ ≃ 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-ASγ 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.
Physical review. D
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
115 Astronomy and space science
The work of A. N. and D. S. was supported by the Ministry of science and higher education of Russian Federation under the Contract No. 075-15-2020-778 in the framework of the large scientific projects program within the national project “Science”.
© 2021 American Physical Society.