ENERGETICS AND LIFETIMES OF LOCAL RADIO ACTIVE GALACTIC NUCLEI

We present a model describing the evolution of Fanaroff-Riley type I and II radio active galactic nuclei (AGNs). and the transition between these classes. We quantify galactic. environments using a semianalytic galaxy formation model. and apply our model to a volume-limited low-redshift (0.03 <= z <= 0.1) sample of observed AGNs to determine the distribution of jet powers and active lifetimes at the present epoch. Radio sources in massive galaxies are found to remain active for longer, spend less time in the quiescent phase, and inject more energy into their hosts than their less massive counterparts. The jet power is independent of the host stellar mass within uncertainties, consistent with maintenance-mode AGN feedback paradigm. The environments of these AGNs are in or close to long-term heating-cooling balance. We also examine the properties of high- and low-excitation radio galactic subpopulations. The HERGs are younger than LERGs by an order of magnitude, whereas. their jet powers are greater by a factor of four. The Eddington-scaled accretion rates and jet production efficiencies of these populations are consistent with LERGs being powered by radiatively inefficient advection-dominated accretion flows, whereas. HERGs are fed by a radiatively efficient accretion mechanism.