The VERITAS Extragalactic Science Program

Abstract: VERITAS is an array of four 12-m diameter imaging atmospheric-Cherenkov telescopes located in southern Arizona. Its aim is to study the very high energy (VHE: E > 100 GeV) gamma-ray emission from astrophysical objects. The study of Active Galactic Nuclei (AGN) is intensively pursued through the VERITAS blazar key science project, but also through the large MWL observational campaigns on radio galaxies. The successful VERITAS AGN research program has provided insights to the jet inner structures and started a more detailed classification of blazars. Moreover, the synergy between Fermi and VERITAS on blazar observations resulted in important constraints on the extragalactic background light (EBL) through gamma-ray observations, and on the cataloguing of the several AGN sub-classes . VERITAS discovered also the first extragalactic non-AGN gamma-ray source. The discovery of gamma-ray emission from the starburst galaxy M 82 by VERITAS and Fermi provides important clues on possible mechanisms for accelerating cosmic rays.