Unbiased Searches for Quasars Beyond a Redshift of 3.5

Abstract

Nearly a decade elapsed between the discovery by Wampler at al. (1973) that the QSO OQ172 has a redshift of 3.53 and the discovery by Peterson et al. (1982) that the QSO Pks 2000–330 has a redshift of 3.78. During that time, radio and optical searches were vigorously pursued to find QSO's with redshifts greater than 3.5, but none were found. In this paper, we discuss selection effects in optical and radio searches and show how these selection effects have limited the redshift range of previous surveys. We propose a combination of radio and optical techniques that may be used to find high redshift QSO's and provide us with an undistorted view of the Universe beyond a redshift of 3.5.