An archival study of IUE observations of low-redshift quasars

The emission-line and continuum characteristics of a sample of 18 low-redshift quasars from the IUE archives are presented. The spectral index $$(F_\nu \propto \nu ^{-\alpha})$$ is found to have a mean value of 1.10±0.11, which is considerably steeper than the index of the same spectral region for high-redshift objects. The line ratios Lα/Hβ and C IV/Lα for the sample, 10.0±2.1 and 0.50±0.04, respectively, are consistent with the value of the photoionization models of Kwan & Krolik. When the low-redshift sample is extended with Seyfert galaxies, intermediate-redshift quasars and high-redshift quasars, the equivalent width of both Lα and C IV anticorrelates with the luminosity at 1450 Å. The slope of the anticorrelation is seen to be steeper for the higher redshift samples than for the low-redshift samples.