The Luminosity Function of z>4 Quasars from the Second Palomar Sky Survey

This paper is the second in a series of papers describing the search for z > 4 quasars using the digitized Second Palomar Sky Survey. This is a photographic multicolor search in three bands, JFN, calibrated to Gunn- Thuan gri, over the range 16. 5ᵐ^ < r < 19. 6ᵐ^. In the first paper, the search techniques were described and the discovery of our first six quasars (five previously unknown) was reported. Here we report the discovery of four additional new quasars, and present coordinates, finding charts, and spectra for these objects. In addition, we describe our adopted candidate selection procedures developed in light of our initial discoveries. The selection criteria have been applied objectively to our data sets, allowing us to estimate our survey completeness through Monte Carlo simulations, and calculate quasar space densities at high redshift. So far, we have covered 27 plate fields, for an effective area of 681 deg²^. Follow-up spectroscopy is complete for large portions of the color-color space. At our median redshift of z = 4. 35, we find that quasar space densities are down by a factor of 7 from z 2. 0, and we see no evidence for luminosity dependent density evolution from z = 2 to z =4. We discuss how these findings compare to other surveys for quasars at high redshift.