© Vaidehi S. Paliya and Dhruba Saikia

Active galaxies are broadly divided into active galactic nuclei (AGN) whose primary energy source is accretion onto supermassive black holes, and the starburst galaxies which undergo intense bursts of star formation. These active galaxies, especially AGN, are amongst the largest and most luminous sources in our Universe. They emit across the electromagnetic spectrum, and pose a number of interesting astrophysical questions. A few active galaxies are also either confirmed or strong candidates for neutrino emission. This seminar will discuss our current understanding of these sources from observations at the low-energy radio waves and the highest energy gamma rays. It will introduce the rich diversity of active galaxies which emit gamma rays, and briefly discuss possible physical processes responsible for their high energy emission.