A wide-field multicolor survey for high-redshift quasars, Z greater than or equal to 2.2. 3: The luminosity function

In two previous papers we presented the aims, methods, and spectroscopic results, and computed the completeness of a six-band multicolor survey for high-redshift quasars, covering an effective area of 43. 0 deg²^, to mₒr_ = 20. 0. In this paper the complete sample of 86 quasars 2. 2 3. 3). These limits include an allowance for the uncertainty in the estimate of the luminosity function at z = 3. 3. Our results are very similar to those obtained by Osmer a decade ago. A similar comparison against the preliminary results of the brighter survey of Irwin et al. indicates that the amount of the decline is approximately independent of absolute magnitude, brighter than the above limits. The observed decline in the space density of quasars beyond z = 3. 3 is compatible with a constant true space density and obscuration by dust in intervening damped Lyα systems only if the parameters of the obscuration (dust to gas ratio, etc. ) are at the upper end of current observational limits. The line luminosity function at z = 3 and 4 is computed, to compare against the forthcoming results of the wide-field grism survey of Schmidt et al.