IUE observations of high-redshift quasars.

Abstract

The authors have measured the continuum energy distributions of nine high-redshift quasars (1.0 ≤ z ≤ 2.2) with the IUE and the Palomar 5 m multichannel spectrophotometer. Generally, the spectral energy distributions steepen at a rest wavelength of about 1200 Å, from a power law, in the optical, of spectral index α ≈ -0.5, to a spectral index of -3 to -5 shortward of 1200 Å. An extensive discussion of the physical causes of this spectral steepening is presented. Six of the spectra exhibit a total of nine optically thick Lyman limit discontinuities with z_abs very low z_em. Eight out of nine of the systems surveyed have associated Mg II or C IV doublets, with physical parameters consistent with the hypothesis that the absorbing material is associated with a galactic halo or disk.