Survey for Very Faint Quasars

类星体(类星体，或类星体)最引人注目的方面之一是它们随着宇宙时间的强烈集体演化，从近距离和远距离样本的比较中可以明显看出这一点。类星体发光阶段的持续时间可能很短，不到1亿年，因为否则中心质量会变得不合理地大。另一方面，集体进化的时间尺度显然比10亿年要长得多。因此，理解类星体的一个基本问题是，是什么决定了它们各自的出生和死亡，以及是什么控制了类星体在宇宙年龄段的整体活动。如果能够获得更清晰的集体演化图景，就有可能更好地理解类星体的性质以及它们与星系起源的关系。这项研究将通过扩展和阐述一种经过验证的探测技术来提供关于非常微弱的类星体的基本数据，这种探测技术使我们有可能实现比任何其他探测都更暗的极限和更高的已确认类星体的表面密度。测量技术包括高精度、宽视场、多波段的光度测量来识别类星体候选，然后对这些候选进行多目标光谱测量以获得红移。其目的是确定低亮度类星体到极高红移的演化特征。这一信息是对广域(施密特)望远镜在更明亮的极限下获得的高亮度类星体的补充。

One of the most striking aspects of quasi-stellar objects (quasars, or QSOs) is their strong collective evolution with cosmic time, as is apparent from a comparison of near and distant samples. The duration of the luminous phase of quasars is likely to be short, less than 100 million years, because otherwise the central masses would become unreasonably large. On the other hand, the collective evolution evidently has a timescale that is much longer than 1 billion years. A basic question in understanding quasars is thus what governs their individual births and deaths, and what controls the overall activity of quasars over the age of the universe. If a clearer picture for the collective evolution can be obtained, it is possible that the nature of quasars, and their relation to the origin of galaxies, can be better understood. The research will provide fundamental data on very faint quasars by expanding and elaborating on a proven survey technique that has made it possible to achieve fainter limits and a higher surface density of confirmed quasars than any other survey. The survey technique involves high-precision, wide-field, multi-band photometry to identify quasar candidates, followed by multi-object spectroscopy of these candidates to obtain redshifts. The objective is to determine the evolutionary characteristics of low-luminosity quasars up to very high redshifts. This information complements that obtained for high-luminosity quasars by wide-field (Schmidt) telescopes at brighter limits.