LINE-PROFILES AND THE KINEMATICS OF THE NARROW-LINE REGION IN SEYFERT-GALAXIES

We have obtained high signal-to-noise ratio, long-slit CCD spectra at ≈ 100 km s-1 resolution for six high-ionization Seyfert galaxies. By subtracting the stellar absorption features with the aid of continuum templates, and using deblending techniques, we were able to measure the asymmetry indices of a number of optical emission-line profiles spanning a wide range in both ionization potential and critical density in each galaxy. These measurements are used to study the fundamental problem of the direction of cloud motion in the narrow-line region (NLR) on the assumption that the preponderance of blueward profile asymmetries requires both radial motion and a source of extinction. We argue by means of simple, spherically symmetric NLR simulations that infall and outflow models can be distinguished by comparing asymmetry indices as a function of ionization potential and critical density. We confirm the positive correlation found by De Robertis and Osterbrock (at lower spectral resolution) between line width and ionization potential and/or critical density for these galaxies. We find positive correlations between the asymmetry index and both ionization potential and critical density. As well, profiles with low ionization potential and critical density have low, but usually nonzero, asymmetry indices. These results are most easily understood in terms of a simple NLR model in which the extinction arises primarily within radially infalling clouds; the alternative possibility of extinction arising between outflowing clouds cannot be entirely ruled out, but it is much more difficult to reconcile with these observations.