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It is generally accepted in the astronomical comunity that radio galaxies correspond to the first ranked elliptical galaxies in groups of galaxies. Here we analyze this statement in more detail.
We find that indeed the magnitudes of radio galaxies are as bright as is expected for first ranked ellipticls in groups. However, we show from the surface brightness profiles of radio galaxies that only 17% of them resemble elliptical galaxies.
Distinguishing between Faranoff Riley type I and II sources, we find that the FRIs are on average brighter than the FRIIs and that they reside on average in richer groups than the FRIIs. The morphologies of the underlying galaxies are also different. About 2/3rds of the FRIs are found in cD, D or in dumbell galaxies while the FRIIs avoid this type of environment. Instead, many of the FRIIs are found in rather disturbed elliptical-like galaxies or in N-galaxies.
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