The color selection of quasars from redshifts 5 to 10: Cloning and discovery

We present simulations of quasar colors, magnitudes, and numbers at redshifts 5 < z < 10 based on our discovery of 10 new high-redshift quasars and the cloning of lower redshift Sloan Digital Sky Survey (SDSS) quasars. The 10 quasars have redshifts ranging from z = 4.7 to 5.3 and i magnitudes of 20.21-20.94. The natural diversity of spectral features in the cloned sample allows more realistic simulation of the quasar locus width than was previously possible with synthetic template spectra. Colors are generated for the z > 6 epoch, taking advantage of the new UKIRT Infrared Deep Sky Survey near-infrared filter set, and we examine the redshift intervals of maximum productivity, discussing color selection and survey depth issues. On the basis of the SDSS sample, we find that the surface density of z > 4.7 quasars increases by a factor of 3 times by extending 0.7 i magnitudes deeper than the SDSS spectroscopic survey limit of i = 20.2; correspondingly, we predict a total of ∼400 faint quasars in the SDSS main area that have redshift z > 4.7 and magnitudes i < 20.9.