Cold-gas outflows in typical low-redshift galaxies are driven by star
  formation, not AGN
  Energetic feedback from active galactic nuclei (AGN) is an important
ingredient for regulating the star-formation history of galaxies in models of
galaxy formation, which makes it important to study how AGN feedback actually
occurs in practice. In order to catch AGNs in the act of quenching star
formation we have used the interstellar NaD absorption lines to look for
cold-gas outflows in a sample of 456 nearby galaxies for which we could
unambigously ascertain the presence of radio AGN activity, thanks to radio
imaging at milli-arcsecond scales. While compact radio emission indicating a
radio AGN was found in 103 galaxies (23% of the sample), and 23 objects (5%)
exhibited NaD absorption-line kinematics suggestive of cold-gas outflows, not
one object showed evidence of a radio AGN and of a cold-gas outflow
simultaneously. Radio AGN activity was found predominantly in early-type
galaxies, while cold-gas outflows were mainly seen in spiral galaxies with
central star-formation or composite star-formation/AGN activity. Optical AGNs
also do not seem capable of driving galactic winds in our sample. Our work adds
to a picture of the low-redshift Universe where cold-gas outflows in massive
galaxies are generally driven by star formation and where radio-AGN activity
occurs most often in systems in which the gas reservoir has already been
significantly depleted.
