Observational Studies of High Redshift Quasars

类星体的红移截止将通过对高红移类星体的系统巡天来研究。已知给定光度的类星体数量随着红移的增加而增加。然而，在红移超过2.5或3之后，类星体的数量就会减少。这一现象可能标志着宇宙大爆炸后大约20亿年，类星体在宇宙中首次出现。目前，类星体数量在高红移时的下降鲜有文献记载。这些类星体非常罕见。通常在天空的一万颗恒星中会发现一颗高红移类星体。这项调查技术将包括用帕洛马的200英寸望远镜记录大约100万个微弱物体的低色散光谱。显示发射线的对象将被选中。所有发射线天体的后续光谱将显示这些天体中哪些是类星体，并测量它们的红移。通过对调查的仔细控制和校准，将有可能评估其完整性极限，从而对高红移类星体进行定量普查。这些结果将允许对解释早期宇宙中突然出现的类星体的不同假设进行评估。这种现象很可能与星系的诞生有关。

The redshift cutoff of quasars will be studied by carrying out systematic surveys for high-redshift quasars. It is known that the number of quasars of given luminosity increases with increasing redshift. Beyond a redshift of 2.5 or 3, however, there is a drop in quasar numbers. This phenomenon probably signifies the first appearance of quasars in the universe, about 2 billion years after the Big Bang. At the present time the drop in quasar numbers at high redshift is poorly documented. These quasars are very rare. Typically one high-redshift quasar is found among 10,000 stars in the sky. The survey technique will involve video recording the low-dispersion spectra of approximately 1 million faint objects with the 200-inch telescope at Palomar. The objects that show emission lines will be selected. Follow-up spectroscopy of all the emission-line objects will show which of these objects are quasars as well as measure their redshifts. By careful control and calibration of the survey, it will be possible to evaluate its completeness limits, and thus conduct a quantitative census of high-redshift quasars. The results will allow the evaluation of different hypotheses proposed to explain the sudden appearance of quasars in the early universe. This phenomenon may well be associated with the birth of galaxies.