Theoretical Models of Active Galactic Nuclei

This paper reviews attempts to incorporate radio sources within the context of general models of active galactic nuclei. The behaviour of gas accreting onto a massive black hole depends upon its angular momentum and accretion rate. It is argued that radio galaxies, QSR's and QSO's be associated with increasing mass accretion rates M/M. The classification of an active galaxy appears to be aspect-dependent. In particular BL Lac objects, OVV quasars and the superluminally expanding compact sources appear to be beamed towards us. It is shown how the choice of source model can influence the statistics of beaming.