The Molecular Gas Content of z<0.1 Radio Galaxies: Linking the AGN
  Accretion Mode to Host Galaxy Properties
  One of the main achievements in modern cosmology is the so-called `unified
model', which successfully describes most classes of active galactic nuclei
(AGN) within a single physical scheme. However, there is a particular class of
radio-luminous AGN that presently cannot be explained within this framework --
the `low-excitation' radio AGN (LERAGN). Recently, a scenario has been put
forward which predicts that LERAGN, and their regular `high-excitation' radio
AGN (HERAGN) counterparts represent different (red sequence vs. green valley)
phases of galaxy evolution. These different evolutionary states are also
expected to be reflected in their host galaxy properties, in particular their
cold gas content. To test this, here we present CO(1-0) observations toward a
sample of 11 of these systems conducted with CARMA. Combining our observations
with literature data, we derive molecular gas masses (or upper limits) for a
complete, representative, sample of 21 z<0.1 radio AGN. Our results yield that
HERAGN on average have a factor of ~7 higher gas masses than LERAGN. We also
infer younger stellar ages, lower stellar, halo, and central supermassive black
masses, as well as higher black hole accretion efficiencies in HERAGN relative
to LERAGN. These findings support the idea that high- and low-excitation radio
AGN form two physically distinct populations of galaxies that reflect different
stages of massive galaxy build-up.
