The EDGE-CALIFA Survey: Central molecular gas depletion in AGN host
  galaxies -- a smoking gun for quenching?
  Feedback from an active galactic nucleus (AGN) is often implicated as a
mechanism that leads to the quenching of galactic star formation. However,
AGN-driven quenching is challenging to reconcile with observations that AGN
hosts tend to harbour equal (or even excess) amounts of gas compared with
inactive galaxies of similar stellar mass. In this paper, we investigate
whether AGN feedback happens on sub-galactic (kpc) scales, an effect that might
be difficult to detect with global gas measurements. Using kpc-scale
measurements of molecular gas (Sigma_H2) and stellar mass (Sigma_*) surface
densities taken from the EDGE-CALIFA survey, we show that the gas fractions of
central AGN regions are typically a factor of ~2 lower than in star-forming
regions. Based on four galaxies with the best spaxel statistics, the difference
between AGN and star-forming gas fractions is seen even within a given galaxy,
indicating that AGN feedback is able to deplete the molecular gas reservoir in
the central few kpc.
