  We have used the VLBA at 5 GHz to observe all galaxies with nuclear radio
flux densities above 3.5 mJy found in a VLA survey at 15 GHz of a sample of
nearby LINER galaxies. All galaxies were detected revealing high brightness
temperature ($T_{b} \ga 10^8$ K) radio sources. Free-free emission is unlikely
since it greatly overpredicts the soft X-ray luminosities. We infer the
presence of AGN-like, non-thermal radio emission most likely powered by
under-fed black holes. Together with our VLA sample we estimate from our
observations that at least half of LINER galaxies host genuine AGN. We find no
evidence for highly inverted radio cores as predicted in the ADAF model: the
(non-simultaneous) spectral indices are on average around $\alpha=0.0$. In the
two brightest sources we detect some extended emission, which appears to
originate in jets in at least one of these galaxies. Together with the spectral
indices this suggests that the nuclear emission at centimeter radio waves is
largely dominated by emission from radio jets, very similar to the situation in
more luminous AGN. The energy released in these jets could be a significant
fraction of the energy budget in the accretion flow.

Astrophysics