Bubbles, jets, and clouds in active galactic nuclei

Analytic calculations are presented for all aspects of the Blandford and Rees (1974) fluid twin-exhaust model for jet formation, with attention to nonrelativistic cavity nozzle structures: the preshock flow, the central shock, the cavity flow, and the nozzle. It is found that for a given central confining gas cloud, only a finite range of jet powers is possible, and that the sound speed ratio between cavity and cloud must be less than 30. Central masses of about one billion solar masses within 1 pc are required for 10 to the 46th ergs/sec extragalactic jets. The critical dependence of jet power on confining cloud sound speed allows a schematization of galactic nuclei to be proposed. Seyfert galaxies and quasars are placed in the low luminosity bubble regime, and variable compact radio sources reach the cloud regime. Evolutionary paths are suggested which may provide an indirect test of this schematization.