An Ultraviolet Atlas of Quasar and Blazar Spectra

We have constructed an ultraviolet atlas of 69 quasars, blazars, and Seyfert 1 galaxies by combining over 1000 low-resolution spectra drawn from over a decade of observations contained in the IUE data archive. In order to optimize the signal-to-noise ratio, the spectra have been reextracted and co-added. The IUE spectra show that quasars and blazars vary more in the ultraviolet than in the optical; 35% of the quasars and 55% of the blazars varied by over a factor of 2 in these observations. Our data show increasing variability toward shorter wavelengths. The high degree of variability at UV wavelengths suggests that projects monitoring gravitational lenses for time delays would benefit from synoptic UV data. The low-redshiftl quasars have Lyα emission lines dominated by strong, narrow components, while high-redshift quasars seem to lack such narrow components. Twelve quasars and six blazars are observed below the Lyman limit. There is no evidence for Lyman edges from accretion disks and very little evidence for Lyman edges caused by broad line clouds intercepting the line of sight. A number of absorption phenomena are found in the spectra. Absorption by gas in our Galaxy is ubiquitous in the strong interstellar lines of C II, O I, Si II, Mg II, and Fe II. In some sightlines, there is indirect evidence that absorption is detected from high-velocity Galactic clouds. Several quasars show the Galactic λ2200 diffuse feature from dust. Intervening absorption is detected in a few of the quasars which are situated close to foreground galaxies. Of special note is the detection of Fe II and Mg II absorption due to gas associated with NGC 3067 in the quasar 3C 232. Over 20% of the combined quasar and Seyfert 1 sample show either associated absorption, or absorption just shortward of the emission redshift; two are broad absorption line quasars. A much smaller number(about 9%) show intervening absorption with Z_abs_<< Z_em_. There are 15 strong unidentified absorption lines in eight objects in the sample. Nine of the 15 lines could be Lyα absorption at redshifts lower than the emission redshift of the background object. This atlas will be useful as a reference for future ultraviolet studies of these objects, especially with the Hubble Space Telescope.