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.
