We present evidence that the outflowing UV absorbers in Seyfert 1 galaxies arise primarily in their inner narrow ( emission ) line regions ( NLRs ) , based on similarities in their locations , kinematics , and physical conditions .
1 ) Hubble Space Telescope observations show that nearly all Seyfert galaxies have bright , central knots of [ O III ] emission in their NLRs with radii of tens of parsecs .
These sizes are consistent with most previous estimates of the distances of UV ( and X-ray ) absorbers from their central continuum sources , and a recently-obtained reliable distance of \sim 25 pc for a UV absorber in the Seyfert 1 galaxy NGC 3783 .
2 ) The nuclear emission-line knots in a sample of 10 Seyfert galaxies have velocity widths of 300 – 1100 km s ^ { -1 } ( half-width at zero intensity ) , similar to the radial velocities of most UV absorbers .
The highest radial velocity for a Seyfert UV absorber to date is only - 2100 km s ^ { -1 } , which is much lower than typical broad-line region ( BLR ) velocities .
There is also mounting evidence that the NLR clouds are outflowing from the nucleus , like the UV absorbers .
3 ) If our hypothesis is correct , then the NLR should have a component with a high global covering factor ( C _ { g } ) of the continuum source and BLR , to match that found from previous surveys of UV absorbers ( C _ { g } = 0.5 – 1.0 ) .
Using STIS spectra of NGC 4151 , obtained when the continuum and BLR fluxes were low , we find evidence for optically thin gas in its nuclear emission-line knot .
We are able to match the line ratios from this gas with photoionization models that include a component with C _ { g } \approx 1 and an ionization parameter and hydrogen column density that are typical of UV absorbers .