THE INFLUENCE OF QSO EMISSION-LINE VELOCITY SHIFTS ON ESTIMATES OF THE INTERGALACTIC BACKGROUND INTENSITY

Observations of the Inverse Effect indicate that the observed number o f QSOs cannot provide sufficient radiation to reionize the intergalact ic medium. We reanalyze the data set of one such study and show that b ias in the measurement of QSO redshifts can account for at least a pro portion of the discrepancy between the observed and predicted ionizing background when current QSO luminosity evolution models are used. The exact value of the shortfall depends on the assumed opacity due to in tervening absorption systems, but for one optically thick model our re assessment indicates that the apparent discrepancy between the observe d ionizing background strength and that predicted from ''QSO-only'' mo dels is halved. This result places ionization models which solely invo lve QSO ionizing radiation within a factor of almost-equal-to 4 of sup plying all the photons required by the observations and may be within a factor of 2 if the opacity of the universe has been overestimated in current models. When account is taken of the incompleteness of the QS O luminosity function at high redshift, it is quite possible that the bulk of the intergalactic ionizing radiation is provided by active gal actic nuclei.