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Relativistic jets - Radiatively inefficient AGN There...

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Relativistic jets At least some accretion discs produce jets , twin highly collimated and fast outflows that emerge in opposite directions from close to the disc (the direction of the jet ejection must be determined either by the angular momentum axis of the disc or the spin axis of the black hole). The jet production mechanism and indeed the jet composition on very small scales are not known at present, as observations cannot distinguish between the various theoretical models that exist. The jets have the most obvious observational effects in the radio waveband, where Very Long Baseline Interferometry can be used to study the synchrotron radiation they emit down to sub- parsec scales. However, they radiate in all wavebands from the radio through to the gamma-ray via the synchrotron and inverse-Compton process, and so AGN with jets have a second potential source of any observed continuum radiation.
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Unformatted text preview: Radiatively inefficient AGN There exists a class of 'radiatively inefficient' solutions to the equations that govern accretion. The most widely known of these is the Advection Dominated Accretion Flow (ADAF), [4] but others exist. In this type of accretion, which is important for accretion rates well below the Eddington limit , the accreting matter does not form a thin disc and consequently does not radiate away the energy that it has acquired in moving close to the black hole. Radiatively inefficient accretion has been used to explain the lack of strong AGN-type radiation from massive black holes in the centres of elliptical galaxies in clusters, where otherwise we might expect high accretion rates and corresponding high luminosities. [5] Radiatively inefficient AGN would be expected to lack many of the characteristic features of standard AGN with an accretion disc....
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