Discovering AGN-driven winds through their infrared emission: I. General
  method and wind location
  Large scale outflows of different gas phases are ubiquitous in the host
galaxies of active galactic nuclei (AGN). Despite their many differences, they
share a common property - they all contain dust. The dust is carried with the
outflow, heated by the AGN, and emits at infrared wavelengths. This paper shows
that the infrared emission of this dust can be used to detect AGN outflows and
derive their properties. We use a sample of about 4000 type II AGN and compare
the infrared properties of systems that show spectroscopic signature of ionized
gas outflows to systems that do not. We detect an additional mid-infrared
emission component in galaxies with spectroscopically discovered winds, and
attribute it to the dust in the outflow. This new component offers novel
constraints on the outflow properties, such as its mean location and covering
factor. We measure the location of the outflow for roughly 1700 systems, with
the distribution showing a prominent peak around 500 pc, a tail that extends to
large distances (10 kpc), and no objects with a location smaller than 50 pc.
The covering factor of the wind shows a wide distribution which is centered
around 0.1, with 24% (8%) of the winds showing covering factors larger than 0.2
(0.5). The dust emission is not sensitive to various systematics affecting
optically-selected outflows, and can be used to estimate the mass outflow rate
in thousands of galaxies with only 1D spectra.
