Stochastic acceleration of cosmic rays in the central molecular zone of the galaxy

Abstract

Particle acceleration in the inner ∼200 pc of the Galaxy is discussed, where diffuse TeV γ-rays have been detected by High Energy Stereoscopic System observations. Diffuse γ-ray emission has a strong correlation with molecular clouds with large velocity dispersion, indicating the presence of turbulence. It is argued that turbulence may contribute to the acceleration of cosmic rays via stochastic acceleration. 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 diffuse TeV γ-ray emission. © 2011. Astronomical Society of Japan.