Simulation of Cosmic Ray propagation in the Galactic Centre Ridge in Accordance with Observed VHE gamma-ray Emission

TL;DR

This paper models cosmic ray diffusion in the Galactic Centre, matching observed gamma-ray emissions to determine the most probable diffusion parameters and their energy dependence.

Contribution

It presents the first time-dependent simulations to estimate the cosmic ray diffusion coefficient in the Galactic Centre region based on gamma-ray observations.

Findings

Optimal diffusion coefficient values identified for the region.

Energy dependence of diffusion characterized by specific parameters.

Cosmic ray origin likely from a central point 10 kyr ago.

Abstract

Diffuse VHE gamma radiation from the Galactic Centre ridge observed by the H.E.S.S. telescope has been convincingly linked with the propagation of recently accelerated cosmic rays that interact with molecular hydrogen clouds during their diffusion. Through a series of time-dependent simulations of that diffusion for different propagation parameters we have obtained the most probable values of the diffusion coefficient for the Galactic Centre region. Assuming that the diffusion coefficient is of the form kappa(E) = kappa_0*(E/E_0)^delta, then for different optimal combinations of kappa_0 and delta its value is obtained for cosmic rays originating from a central point (possibly Sgr A East) 10 kyr ago.