Signatures of anisotropic diffusion around PeVatrons in 100 TeV gamma-ray data

TL;DR

This paper explores how anisotropic diffusion of PeV cosmic rays along the Galactic magnetic field can explain the extended gamma-ray emission observed by Tibet ASγ, providing insights into cosmic ray propagation and sources.

Contribution

It demonstrates that anisotropic diffusion can produce extended gamma-ray sources consistent with observations, offering a new method to study cosmic ray diffusion and identify PeVatrons.

Findings

Anisotropic diffusion can explain extended gamma-ray emission.

Extended sources can be used to study cosmic ray propagation.

Results are consistent with Tibet ASγ measurements.

Abstract

The Tibet AS$\gamma$ collaboration has reported a diffuse $\gamma$-ray emission signal from the Galactic Plane. We consider the possibility that the diffuse emission from the outer Galactic Plane at the highest energies is produced by cosmic rays spreading from a single supernova-type source either in the Local or Perseus arm of the Milky Way. We show that anisotropic diffusion of multi-PeV cosmic rays along the Galactic magnetic field can produce an extended source spanning ten(s) of degrees on the sky, with a flux-per-unit-solid-angle consistent with Tibet AS$\gamma$ measurements. Observations of this new type of very extended sources, and measurements of their morphologies, can be used to characterize the anisotropic diffusion of PeV cosmic rays in the Galactic magnetic field, and to constrain the locations and properties of past PeVatrons.