Stochastic Acceleration of Cosmic Rays in the Central Molecular Zone of the Galaxy

TL;DR

This paper explores how turbulence-driven stochastic acceleration in the Galaxy's central molecular zone can energize cosmic rays, explaining observed diffuse TeV gamma-ray emissions through a hadronic process.

Contribution

It presents a model where turbulence in the central molecular zone accelerates cosmic rays, supporting the hadronic origin of gamma-ray emission.

Findings

Cosmic-ray protons can reach energies up to ~100 TeV.

Electrons can be accelerated up to ~1 TeV.

Turbulence correlates with observed gamma-ray emission.

Abstract

Particle acceleration in the inner ~ 200 pc of the Galaxy is discussed, where diffuse TeV gamma-rays have been detected by the High Energy Stereoscopic System (HESS) observation. The diffuse gamma-ray emission has a strong correlation with molecular clouds with large velocity dispersion, indicating the presence of turbulence. It is argued that the turbulence may contribute to the acceleration of cosmic rays via stochastic acceleration. The stochastic acceleration may energize cosmic-ray protons up to ~ 100 TeV and electrons to ~ 1 TeV in a relatively tenuous medium. The difference in the efficiency between protons and electrons supports the hadronic scenario of the diffuse TeV gamma-ray emission.