AAS Meeting #193 - Austin, Texas, January 1999
Session 6. Nearby AGN I - Dust, Gas, Obscuration and Fuelling
Display, Wednesday, January 6, 1999, 9:20am-6:30pm, Exhibit Hall 1

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[6.14] Properites of the Intrinsic Absorption in NGC 5548

D.M. Crenshaw, S.B. Kraemer (CUA/GSFC)

We present a detailed study of the physical conditions and kinematics of the intrinsic absorbing material near the nucleus of the Seyfert 1 galaxy NGC~5548. The study is based on UV spectra obtained at high resolution (R = 20,000 -- 40,000), which is needed to resolve the kinematic components of the absorption lines. Echelle spectra over the entire UV band were obtained with the Space Telescope Imaging Spectrograph (STIS) on 1998 March 11, and compared to Goddard High Resolution Spectrograph (GHRS) observations of the N~V region on 1996 February 16 and the C~IV region on 1996 August 24. We have identified five distinct kinematic components in the absorption lines of L\alpha, C~IV \lambda\lambda1548.2, 1550.8, and N~V~\lambda\lambda1238.8, 1242.8 at radial velocities of -160 to -1060 km s-1 with respect to the nucleus. There is an additional L\alpha component near the systemic velocity, which may be due to the interstellar medium in the host galaxy.

We have determined covering factors (in the line-of-sight) and column densities for all of the components. We have also placed upper limits on the column densities of Si~IV and Mg~II absorption. We find evidence for variations in the column densities of N~V and C~IV over two years for two of the kinematic components, but no evidence for changes in the radial velocity coverage of any component. We use these measurements and photoionization models to investigate the physical conditions in the different kinematic components of the absorbing gas.

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