Radial Velocity Offsets Due to Mass Outflows and Extinction in Active
  Galactic Nuclei
  We present a study of the radial velocity offsets between narrow emission
lines and host galaxy lines (stellar absorption and H I 21-cm emission) in
Seyfert galaxies with observed redshifts less than 0.043. We find that 35% of
the Seyferts in the sample show [O III] emission lines with blueshifts with
respect to their host galaxies exceeding 50 km/s, whereas only 6% show
redshifts this large, in qualitative agreement with most previous studies. We
also find that a greater percentage of Seyfert 1 galaxies show blueshifts than
Seyfert 2 galaxies. Using HST/STIS spatially-resolved spectra of the Seyfert 2
galaxy NGC 1068 and the Seyfert 1 galaxy NGC 4151, we generate geometric models
of their narrow-line regions (NLRs) and inner galactic disks, and show how
these models can explain the blueshifted [O III] emission lines in collapsed
STIS spectra of these two Seyferts. We conclude that the combination of mass
outflow of ionized gas in the NLR and extinction by dust in the inner disk
(primarily in the form of dust spirals) is primarily responsible for the
velocity offsets in Seyfert galaxies. More exotic explanations are not needed.
We discuss the implications of this result for the velocity offsets found in
higher redshift AGN.
