FOS Spectroscopy of the Seyfert 1 Galaxy NGC 5548
Session 4 -- AGNs
Display presentation, Monday, 9:20-6:30, Pauley Room

## [4.04] FOS Spectroscopy of the Seyfert 1 Galaxy NGC 5548

D.M. Crenshaw (CSC), A. Boggess (NASA/GSFC), C.-C. Wu (CSC)

Ultraviolet spectra of the Seyfert 1 galaxy NGC 5548 have been obtained with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope. The observations were made at a time when the UV continuum and broad emission lines were at their lowest ever observed level. The high resolution of the spectra (R = 1000), and the low continuum and broad-line flux levels allow for a clean separation of the broad and narrow components of L$\alpha$, C IV $\lambda$1549, and C~III] $\lambda$1909. Relative to the other UV narrow lines, C IV is much stronger in NGC 5548 than in Seyfert 2 galaxies observed with IUE, which indicates that the average ionization parameter is higher in the narrow-line region (NLR) of NGC 5548. The narrow component of Mg II $\lambda$ 2798 is very weak in NGC 5548, which suggests that the NLR clouds are fully ionized and lack substantial transition zones'' that produce the majority of this line in Seyfert 2 galaxies. Thus, it appears the the NLR clouds in NGC 5548 experience a higher level of ionizing flux, on average, than those in Seyfert 2 galaxies.