FAINT OBJECT SPECTROGRAPH SPECTRA OF THE UV EMISSION-LINES IN NGC-5548 - DETECTION OF STRONG NARROW COMPONENTS

Ultraviolet spectra of the Seyfert 1 galaxy NGC 5548 were obtained wit h the Faint Object Spectrograph (FOS) on the Hubble Space Telescope on 1992 July 5, when the UV continuum and broad emission lines were at t heir lowest ever observed level. The high resolution of the spectra, r elative to previous UV observations, and the low state of NGC 5548 all ow the detection and accurate measurement of strong narrow components of the emission lines of Lyalpha, C IV lambda1549, and C III] lambda19 09. Isolation of the UV narrow components enables a detailed compariso n of narrow-line region (NLR) properties in Seyfert 1 and 2 galaxies, and removal of their contribution is important for studies of the broa d-line region (BLR). Relative to the other narrow lines, C IV lambda15 49 is much stronger in NGC 5548 than in Seyfert 2 galaxies, and Mg II lambda2798 is very weak or absent.