Absolute spectrophotometry of very large redshift quasars

Absolute spectrophotometric observations of 19 quasars with redshifts greater than 2.66 are reported. Observations were made with a multichannel spectrometer covering wavelengths from 3200 to 10000 A at low resolution and allowing accurate absolute fluxes to be determined for continuum and emission lines. Analysis of energy distribution measurements indicates the continuum spectral index redward of Lyman alpha to vary from -0.2 to -1.2. Average flux levels drop by 29% between Lyman alpha and Lyman beta, and by a further 10% below Lyman beta, and a drop or change of slope occurs near the Lyman limit, all of which are attributed to absorbing clouds at different redshifts. Estimations of a covering factor of 0.08 based on the Lyman alpha and He II 1640 lines are consistent with the production of these lines by recombination. The measured emission lines are observed to have intensities proportional to the continuum flux, with the exception of C IV, which shows the luminosity effect similar to that found by Baldwin (1977).