Survey for Very Faint Quasars

类星体（quasars，或qso）最引人注目的方面之一是它们随着宇宙时间的推移而强烈的集体进化，这一点从近距离和远距离样本的比较中可以明显看出。类星体发光阶段的持续时间很可能很短，少于1亿年，否则中心质量就会变得不合理地大。另一方面，集体进化的时间尺度显然比10亿年长得多。因此，了解类星体的一个基本问题是，是什么控制着它们的个体诞生和死亡，是什么控制着类星体在宇宙年龄期间的整体活动。如果能获得类星体集体演化的更清晰图像，就有可能更好地理解类星体的性质及其与星系起源的关系。这项研究将通过扩展和详细阐述一项经过验证的调查技术，为非常微弱的类星体提供基础数据，该技术使得比其他任何调查都能获得更微弱的极限和更高的表面密度。调查技术包括高精度、宽视场、多波段光度测定来识别类星体候选者，然后对这些候选者进行多目标光谱分析以获得红移。目的是确定低光度类星体直到非常高的红移的演化特征。这个信息补充了宽视场（施密特）望远镜在更亮的极限下获得的高亮度类星体的信息。

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.