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Abstract: The radio luminosity function RLF of radio galaxies and radio-loud quasarsis often modelled as a broken power-law. The break luminosity is close to thedividing line between the two Fanaroff-Riley FR morphological classes for thelarge-scale radio structure of these objects. We use an analytical model forthe luminosity and size evolution of FRII-type objects together with a simpleprescription for FRI-type sources to construct the RLF. We postulate that allsources start out with an FRII-type morphology. Weaker jets subsequentlydisrupt within the quasi-constant density cores of their host galaxies anddevelop turbulent lobes of type FRI. With this model we recover the slopes ofthe power laws and the break luminosity of the RLF determined fromobservations. The rate at which AGN with jets of jet power $Q$ appear in theuniverse is found to be proportional to $Q^{-1.6}$. The model also roughlypredicts the distribution of the radio lobe sizes for FRII-type objects, if theradio luminosity of the turbulent jets drops significantly at the point ofdisruption. We show that our model is consistent with recent ideas of twodistinct accretion modes in jet-producing AGN, if radiative efficiency of theaccretion process is correlated with jet power.

Autor: Christian R. Kaiser Southampton, Philip N. Best Edinburgh


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