Gamma Ray Astronomy: Implications for Fundamental Physics

Gamma Ray Astronomy studies cosmic accelerators through their electromagnetic radiation in the energy range between ∼100 MeV and ∼100 TeV. The present most sensitive observations in this energy band are performed, from space, by the Large Area Telescope onboard the Fermi satellite and, from Earth, by the Imaging Air Cherenkov Telescopes MAGIC, H.E.S.S. and VERITAS. These instruments have revolutionized the field of Gamma Ray Astronomy, discovering different populations of gamma ray emitters and studying in detail the non-thermal astrophysical processes producing this high-energy radiation. The scientific objectives of these observatories include also questions of fundamental physics. With gamma ray instruments we study the origin of Galactic cosmic rays, testing the hypothesis of whether they are mainly produced in supernova explosions. Also, we obtain the most sensitive measurement of the cosmic electron/positron spectrum between 20 GeV and 5 TeV. By observing the gamma ray emission from sources at cosmological distances, we learn about the intensity and evolution of the extragalactic background light, and perform tests of Lorentz Invariance. Moreover, we can search for dark matter by looking for gamma ray signals produced by its annihilation or decay in over-density sites. In this paper, we review the most recent results produced with the current generation of gamma ray instruments in these fields of research.