QUASAR COLORS - STATISTICS AND COSMOLOGICAL EVOLUTION

We have constructed a model spectrum to study QSO broad-band colors as a function of redshift. Using the available statistical data, we have generated realistic color distributions that give quantitative estimates of the incompleteness associated with the various color selection techniques as a function of redshift. We have also developed a simple model for the average Lyman continuum absorption based on the statistics of the Lyα clouds to explore the resulting colors of high-redshift QSOs. Selection biases on the estimate of QSO density at high redshift are also discussed.