Radio constraints on the volume filling factors of AGN winds
  The calculation of mass outflow rates of AGN winds is of great importance in
understanding the role that such winds play in AGN-galaxy feedback processes.
The mass outflow rates are, however, difficult to estimate since the volume
filling factors of the winds are unknown. In this paper, we use constraints
imposed by the observed radio emission to obtain upper limits to the volume
filling factors of wind components in certain nearby AGN. We do this by
predicting the 1.4 GHz radio flux densities emitted by those components,
assuming a uniform wind, and then comparing these with the observed flux
densities for each AGN at this frequency. We find that the upper limits to the
volume filling factors are in the range 10^{-4}-0.5.
