Gravitational Acceleration and Forbidden Line Widths in Seyfert Galaxies

Extract

There now exists extensive data on the forbidden line widths in Seyfert galaxies. While a few Seyferts have anomalously broad lines with FWHM ∼ 500 - 1000 km s⁻¹ (e.g. NGC 1068, MKN 3, MKN 78), the majority have narrower lines with FWHM ∼ 200 - 400 km s⁻¹. Although these line widths are well known to be of Doppler origin, the physical processes responsible for accelerating the gas have yet to be clearly identified. Processes associated with the activity itself are suggested by the large linewidths of the broadest profiles as well as by the presence of a correlation between [OIII] FWHM and steep spectrum radio luminosity. On the other hand, the prevelence of narrower lines and total absence of correlation between [OIII] FWHM and overall level of activity (Seyfert 2s, Seyfert 1s, and QSOs) suggests that more normal, possibly gravitational, processes are important. To test this latter possibility, it is necessary to look for explicit correlations between [OIII] FWHM and diagnostics of galactic gravitational potential.