Some galaxies are very bright in radio waves compared to normal galaxies. When these radio galaxies are mapped, we see most of the emission is coming from radio lobes that look like larger versions of the bipolar flows from young stars or in the formation of planetary nebulae. So radio galaxies and active galactic nuclei are tied together. Radio maps gave us the details, also images from large optical telescopes show more details. Tiny core, two jets shooting off in opposite directions, two large lobes of radio emission.
Some quasars have the same structure as radio galaxies.
Lots of energy being released, but very small size. The best model that accounts for all the observations is that we're seeing the effects of material falling into a very massive black hole. Gravitational potential energy of matter falling into the black hole gets converted to kinetic energy, which results in more colliding particles, which leads to an increase in thermal energy, which gets carried about by high-energy photons. The x-ray and UV photons generated by the infalling matter will be converted to optical light by the surrounding gas, and to infrared by the dust clouds around it. Jets maybe are caused by strong magnetic fields accelerating particles from the accretion disk and speeding them out from the galaxy.