A Deep Multicolor Survey. II. Initial Spectroscopy and Comparison with Expected Quasar Number Counts

We have used the KPNO 4 m Mayall telescope to image 0. 83 deg²^ of sky in six fields at high Galactic latitude in six filters spanning 3000- 10000 A to magnitude limits ranging from 22. 1 to 23. 8. As a first use of this database, we have conducted a multicolor survey for quasars. We discuss various methods of selecting outliers in different color-color diagrams and multicolor space that have been used to identify quasars at all redshifts from their colors alone. We discuss the initial results of our program of spectroscopic identification which has so far resulted in the identification of over 40 faint quasars, including one at z > 4, a similar number of compact narrow emission-line galaxies, and a number of unusual and potentially interesting stars. We use these spectroscopic results, along with extensive simulations of quasar spectra, to study the efficiency of our candidate selection procedures. Finally, we compare the number counts of our quasars and quasar candidates to the expected numbers based on previous studies of the quasar luminosity function. The agreement of our observations with these expectations is good in most cases. However, we do estimate that our survey contains more quasars with B 3 quasars than expected from the results published by Warren, Hewett, & Osmer in 1994, both at the 3 σ level. Additional spectroscopic observations will be required to confirm or refute these excesses.