Fanaroff Riley Classification
Fanaroff Riley Classification
About
Fanaroff-Riley Class I (FR-I): Sources in this class have their low brightness regions further from the central galaxy or quasar than their high brightness regions. The sources become fainter as one approaches the outer extremities of the lobes and the spectra here are the steepest, indicating that the radiating particles have aged the most. Jets are detected in 80 per cent of FR-I galaxies.
Fanaroff-Riley Class II (FR-II) This class comprises luminous radio sources with hotspots in their lobes at distances from the centre which are such that RFR > 0.5. These sources are called edge-darkened, which was particularly apt terminology when the angular resolution and dynamic range used in observing the classical sources was not always good enough to reveal the hotspots as distinct structures. In keeping with the overall high luminosity of this type of source, the cores and jets in them are also brighter than those in FR-I galaxies in absolute terms; but relative to the lobes these features are much fainter in FR-II galaxies. Jets are detected in < 10 per cent of luminous radio galaxies, but in nearly all quasars
Reading
https://en.wikipedia.org/wiki/Fanaroff%E2%80%93Riley_classification
Experiments