Letter to the Editor

New limit on high Galactic latitude PeV γ-ray flux from Tibet ASγ data

¹ Université de Paris, CNRS, Astroparticule et Cosmologie, 75013 Paris, France
e-mail: andrii.neronov@apc.in2p3.fr
² Astronomy Department, University of Geneva, Ch. d’Ecogia 16, 1290 Versoix, Switzerland
³ Institute for Nuclear Research of the Russian Academy of Sciences, 60th October Anniversary St. 7a, 117312 Moscow, Russia
⁴ Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa City, Chiba 277-8582, Japan

Received: 15 July 2021
Accepted: 30 August 2021

Abstract

The Tibet ASγ collaboration has recently reported the detection of γ-rays with energies up to Peta-electronvolt from parts of the Galactic plane. We note that the analysis of γ-ray flux by the Tibet-ASγ experiment also implies an upper bound on the diffuse γ-ray flux from high Galactic latitudes (|b|> 20°) in the energy range between 100 TeV and 1 PeV. This bound is up to an order of magnitude stronger than previously derived bounds from GRAPES3, KASCADE, and CASA-MIA experiments. We discuss the new Tibet-ASγ limit on the high Galactic latitude γ-ray flux in the context of possible mechanisms of multi-messenger (γ-ray and neutrino) emission from nearby cosmic ray sources, dark matter decays, and the large-scale cosmic ray halo of the Milky Way.