There is a whole class of galaxies that show evidence for very active cores or nuclei. These are commonly called
Active Galactic Nuclei or AGNs.
They include radio galaxies, BL Lacertae objects, and Seyfert galaxies. We now
understand these active galaxies
to be closely related to quasars and to be powered by the same source as for quasars: a
supermassive, rotating black hole in the center of the galaxy.