Intrinsic Absorption Lines in Seyfert 1 Galaxies. I. Ultraviolet Spectra from theHubble Space Telescope

We present a study of the intrinsic absorption lines in the ultravioletspectra of Seyfert 1 galaxies. We find that the fraction of Seyfert 1 galaxiesthat show absorption associated with their active nuclei is more than one-half(10/17), which is much higher than previous estimates (3 - 10%) . There is aone-to-one correspondence between Seyferts that show intrinsic UV absorptionand X-ray ``warm absorbers''. The intrinsic UV absorption is generallycharacterized by high ionization: C IV and N V are seen in all 10 Seyferts withdetected absorption (in addition to Ly-alpha), whereas Si IV is present in onlyfour of these Seyferts, and Mg II absorption is only detected in NGC 4151. Theabsorption lines are blueshifted (or in a few cases at rest) with respect tothe narrow emission lines, indicating that the absorbing gas is undergoing netradial outflow. At high resolution, the absorption often splits into distinctkinematic components that show a wide range in widths (20 - 400 km/s FWHM),indicating macroscopic motions (e.g., radial velocity subcomponents orturbulence) within a component. The strong absorption components have coresthat are much deeper than the continuum flux levels, indicating that theregions responsible for these components lie completely outside of the broademission-line regions. The covering factor of the absorbing gas in the line ofsight, relative to the total underlying emission, is C > 0.86, on average. Theglobal covering factor, which is the fraction of emission intercepted by theabsorber averaged over all lines of sight, is C > 0.5.Comment: 56 pages, Latex, includes 4 figures (encapsulated postscript), Fig. 1 has 2 parts and Fig. 2 has 3 parts, to appear in the Astrophysical Journa