Near-Infrared Surveys for High-Redshift Quasars

AST 95-09919 Because of their great luminosity, quasars can be detected at enormous distances, i.e. high redshift. Surveys for high redshift quasars have already provided a number of new scientific insights. For example, it is now clear that the rapid rise in the density of quasars with increasing distance (decreasing age) halts somewhere between redshifts 2.0 and 3.5, and a recently completed survey has provided evidence that the space density of quasars declines at higher redshifts. Also, there is no significant change with redshift in the strengths of the metal emission lines, indicating that the quasar material has already been enriched by several generations of stellar evolution even at the largest known redshifts. Other surveys are now being carried out to measure the luminosity function of faint quasars via a small-area deep slitless survey, and to search for very high redshift quasars via two large-area surveys, using multicolor CCD images for 4.1 < z < 5.5, and with slitless spectra out to redshifts beyond 6. A catalog will be published for each survey. ***