Gamma-rays from active galactic nuclei

Gamma-ray observations of active galactic nuclei (AGNs) are reviewed and the best candidate mechanisms for gamma ray production in AGNs are examined. Both nonthermal and thermal mechanisms are considered. Hot accretion disks around massive black holes in the centers of AGNs could provide the required thermal electrons, pions, and relativistic lectrons and positrons to explain both the X-ray and gamma emission.