Radio Lobes and [O iii] Profile Substructure in Seyfert Galaxies

High spatial and spectral resolution observations are presented for 10 Seyfert galaxies in the Hβ-[O III] λ5007 spectral region. The Seyfert galaxies were selected to have double or triple radio morphology on scales >0.75". In several cases, there is clear evidence for [O III] λ5007 profile substructure (subpeaks, shoulders) which is more conspicuous close to the positions of the radio lobes. This suggests the presence of two line-emitting constituents in the narrow-line region (NLR): (1) "[O III] components," which are specifically associated with the radio lobes, and (2) "ambient [O III] emission," which is more widely distributed and usually shows normal galactic rotation. A control sample with unresolved or subarcsecond radio morphology shows no evidence for spatially resolved [O III] components. Where possible, the velocity, line width, intensity, and location of these [O III] components have been measured using Gaussian fits to the profile substructure. The relative prominence of the [O III] components varies greatly from object to object, although it is not yet clear what causes this. The gas has high excitation (F_5007_/F_Hβ_ ~ 10-15). When two [O III] components are visible, their velocities fall on either side of the galaxy systemic velocity. The component velocities are usually outside the peak rotation velocities and, in some cases, are opposite to the sense of rotation. This strongly suggests that the [O III] components (and associated radio lobes) do not rotate with the rest of the gas in the galaxy but are instead undergoing systematic outflow. Using the present small sample, several statistical relations have been investigated. There is no tendency for more powerful radio lobes to be associated with either broader [O III] components or more luminous [O III] components. There may be, however, a tendency for broader [O III] components to have both higher bulk velocities, | V(comp)-V(systemic)|, as well as higher [O III] luminosity. These results may be compared with the well-known analogous relations for the integrated NLR properties. Finally, careful measurement of the position of the [O III] components in three galaxies shows that they lie closer to the nucleus than the radio lobes by about 30%.