ABSTRACT
Here we describe the basics of the physical processes that produce cosmic gamma rays. We start with a basic description of how gamma-ray sky maps and the common models for the energy spectral shapes. We then summarize how particles are accelerated to such high energies in shocks using e.g. Fermi Acceleration. Those particles then interact via processes like pion creation, bremsstrahlung, and Compton scattering. We provide an introduction to the physics behind several gamma-ray sources like pulsars, active galactic nuclei, and dark matter. Finally we describe what a statical significance is and how you should interpret ‘3-sigma’ and ‘5-sigma’ signals.
