Radio AGN in the local universe: unification, triggering and evolution
  Associated with one of the most important forms of active galactic nucleus
(AGN) feedback, and showing a strong preference for giant elliptical host
galaxies, radio AGN (L_1.4GHz > 10^24 W Hz^-1) are a key sub-class of the
overall AGN population. Here I review our current state of understanding of the
population of radio AGN at low and intermediate redshifts (z < 0.7),
concentrating on their AGN and host galaxy properties, and covering three
interlocking themes: the classification of radio AGN and its interpretation;
the triggering and fuelling of the jet and AGN activity; and the evolution of
the host galaxies. I show that much of the observed diversity in the AGN
properties of radio AGN can be explained in terms of a combination of
orientation/anisotropy, mass accretion rate, and variability effects. The
detailed morphologies of the host galaxies are consistent with the triggering
of strong-line radio galaxies (SLRG) in galaxy mergers. However, the star
formation properties and cool ISM contents suggest that the triggering mergers
are relatively minor in terms of their gas masses in most cases, and would not
lead to major growth of the supermassive black holes and stellar bulges;
therefore, apart from a minority (<20%) that show evidence for higher star
formation rates and more massive cool ISM reservoirs, the SLRG represent
late-time re-triggering of activity in mature giant elliptical galaxies. In
contrast, the host and environmental properties of weak-line radio galaxies
(WLRG) with Fanaroff-Riley class I (FRI) radio morphologies are consistent with
more gradual fuelling of the activity via gas accretion at low rates onto the
supermassive black holes.
