Nonthermal Emission in the Starburst Galaxies M 82 & NGC 253

Detection of high-energy γ-ray emission from the nearby starburst galaxies M 82 and NGC 253 establishes, for the first time, a direct link between leptonic and hadronic processes in an extragalactic non-AGN environment. We review the most relevant aspects of these processes and contrast theoretical predictions with available radio and γ-ray measurements in order to determine the particle spectral properties and energy densities in these galaxies.