Near-Infrared Surveys for High-Redshift Quasars

类星体由于其巨大的光度，可以在很远的距离，即高红移处被探测到。对高红移类星体的调查已经提供了许多新的科学见解。例如，现在很清楚，类星体的密度随着距离的增加（年龄的减少）而迅速上升，在红移2.0和3.5之间的某个地方停止，最近完成的一项调查提供了证据，证明类星体的空间密度在更高的红移时下降。此外，金属发射线的强度也没有明显的红移变化，这表明类星体物质已经被几代恒星的演化所丰富，即使是在已知最大的红移中。其他的调查现在正在进行，通过小范围的深无缝隙调查来测量微弱类星体的光度函数，并通过两个大范围的调查来搜索非常高的红移类星体，使用4.1 - 5.5的多色CCD图像，并使用红移超过6的无缝隙光谱。每次调查将出版一份目录。＊＊＊

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. ***