  We explore the processes that trigger local AGN and the role of these AGN in
regulating star formation, using ~350 nearby galaxies observed by the mJy
Imaging VLBA Exploration at 20cm (mJIVE) survey. The >10^7 K brightness
temperature required for an mJIVE detection cannot be achieved via star
formation alone, allowing us to unambiguously detect nearby radio AGN and study
their role in galaxy evolution. Radio AGN are an order of magnitude more common
in early-type galaxies (ETGs) than in their late-type counterparts. The
VLBI-detected ETGs in this study have a similar stellar mass distribution to
their undetected counterparts, are typically not the central galaxies of
clusters and exhibit merger fractions that are significantly higher than in the
average ETG. This suggests that these radio AGN (which have VLBI luminosities
>10^22 W Hz^-1) are primarily fuelled by mergers, and not by internal stellar
mass loss or cooling flows. Our radio AGN are a factor of ~3 times more likely
to reside in the UV-optical red sequence than the average ETG. Furthermore,
typical AGN lifetimes (a few 10^7 yr) are much shorter than the transit times
from blue cloud to red sequence (~1.5 Gyr). This indicates that the AGN are not
triggered promptly and appear several dynamical timescales into the associated
star formation episode, implying that they typically couple only to residual
gas, at a point where star formation has already declined significantly. While
evidence for AGN feedback is strong in systems where the black hole is fed by
the cooling of hot gas, AGN triggered by mergers appear not to strongly
regulate the associated star formation. The inability of the AGN to rapidly
quench merger-driven star formation is likely to make merging the dominant mode
of star formation in nearby ETGs, in line with evidence for minor mergers being
the primary driver of stellar mass growth in these systems.
