Quasars and Active Galaxies

What are radio galaxies?

Radio galaxies are simply galaxies—usually very ordinary-looking elliptical galaxies when viewed by visible light—that radiate an unusually large amount of radio waves. Often, the total energy of the radio wave emission far exceeds that of the galaxy’s visible light emission. The majority of the radio wave emission usually comes from huge, puffy “lobes” or narrow “jets” that can be much larger than the visible galaxy itself. The excess radio emission is probably produced when much of the energy generated by an AGN is carried away by highly energetic streams of matter, which then interact with the interstellar medium in and around the host galaxy and cause copious emissions of radio waves.


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