The Energetics and Lifetimes of Local Radio Active Galactic Nuclei
  We present a model describing the evolution of Fanaroff-Riley type I and II
radio AGN, and the transition between these classes. We quantify galaxy
environments using a semi-analytic galaxy formation model, and apply our model
to a volume-limited low redshift ($0.03 \leqslant z \leqslant 0.1$) sample of
observed AGN 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 AGN are in or
close to long-term heating-cooling balance. We also examine the properties of
high- and low-excitation radio galaxy sub-populations. The HERGs are younger
than LERGs by an order of magnitude, whilst 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 (ADAFs), while
HERGs are fed by a radiatively efficient accretion mechanism.
