  It has long been suspected that powerful radio sources may lower the
efficiency with which stars form from the molecular gas in their host galaxy,
but so far, alternative mechanisms, in particular related to the stellar mass
distribution in the massive bulges of their host galaxies, are not ruled out.
We present new ALMA CO(1-0) interferometry of cold molecular gas in the nearby
(z=0.0755), massive (M_stellar=4x10^11 M_sun), isolated, late-type spiral
galaxy 2MASSX J23453269-044925, which is outstanding for having two pairs of
powerful, giant radio jets, and a bright X-ray halo. The molecular gas is in a
massive (M_gas=2x10^10 M_sun), 24 kpc wide, rapidly rotating ring, which is
associated with the inner stellar disk. Broad (FWHM=70-180 km s^-1) lines with
complex profiles associated with the radio source are seen over large regions
in the ring, indicating gas velocities that are high enough to keep the
otherwise marginally Toomre-stable gas from fragmenting into gravitationally
bound, star-forming clouds. About 1-2% of the jet kinetic energy are required
to power these motions. Resolved star-formation rate surface densities fall
factors 50-75 short of expectations from the Kennicutt-Schmidt law of
star-forming galaxies, and near gas-rich early-type galaxies with signatures of
star formation lowered by jet feedback. We argue that radio AGN feedback is the
only plausible mechanism to explain the low star-formation rates in this
galaxy. Previous authors have already noted that the X-ray halo of J2345-0449
implies a baryon fraction near the cosmic average, which is very high for a
galaxy. We contrast this finding with other, equally massive baryon-rich spiral
galaxies without prominent radio sources. Most of the baryons in these galaxies
are in stars, not in the halos. We also discuss the implications of our results
for our general understanding of AGN feedback in massive galaxies.
