Radio galaxy
![False-color image of the nearby radio galaxy Centaurus A, showing radio (red), 24-micrometre infrared (green) and 0.5-5 keV X-ray emission (blue). The jet can be seen to emit synchrotron radiation in all three wavebands. The lobes only emit in the radio frequency range, and so appear red. Gas and dust in the galaxy emits thermal radiation in the infrared. Thermal X-ray radiation from hot gas and non-thermal emission from relativistic electrons can be seen in the blue 'shells' around the lobes, particularly to the south (bottom).](/Images/godic/202501/10/Centauros_a-spc0221.png")
![False-color image of the large-scale radio structure of the FRII radio galaxy 3C98. Lobes, jet and hotspot are labelled.](/Images/godic/202501/10/Radio_galaxy_3C980221.png")
![False-color image of the large-scale radio structure of the FRI radio galaxy 3C31. Jets and plumes are labelled.](/Images/godic/202501/10/Radio_galaxy_3C310222.png")
Radio galaxies and their relatives, radio-loud quasars and blazars, are types of active galaxy that are very luminous at radio wavelengths, with luminosities up to 10 W between 10 MHz and 100 GHz. The radio emission is due to the synchrotron process. The observed structure in radio emission is determined by the interaction between twin jets and the external medium, modified by the effects of relativistic beaming. The host galaxies are almost exclusively large elliptical galaxies. Radio-loud active galaxies can be detected at large distances, making them valuable tools for observational cosmology. Recently, much work has been done on the effects of these objects on the intergalactic medium, particularly in galaxy groups and clusters.