Quasar detection via variability in a high galactic latitude drift scan survey

As part of the QUEST (QUasar E&barbelow;quatorial S&barbelow;urvey T&barbelow;eam) collaboration, I have been studying the intrinsic variability of quasars as a means of quasar detection. I first give a brief review of the quasar central engine that suggests the mechanism driving quasar variability, then report on the current status of the QUEST project as a whole. I discuss the data collection, reduction and analysis program, and the findings over the course of three observing seasons (February 1999–April 2001) at the 1-m Schmidt telescope at the Venezuelan National Observatory. The method of incomplete ensemble photometry was used to compile a list of variable objects from these data. I then describe the subsequent spectroscopic confirmation work carried out at the WIYN 3.5-m telescope in April 2001 and February 2002. (The WIYN Observatory is a joint facility of the University of Wisconsin-Madison, Indiana University, Yale University, and the National Optical Astronomy Observatory.) Between the two spectroscopic observing campaigns, 30 of a selected subset of variable objects were identified as quasars by means of their distinctive spectral emission lines, 50% of which are newly discovered quasars and 50% of which are independent rediscoveries of previously cataloged quasars.; The number of previously cataloged quasars found in the data is used as a benchmark for statistical analysis and to predict what percentage of variability candidates should be expected to be confirmed as quasars. The percentage of known quasars that vary is seen to increase when comparing data from two observing seasons (38%) with data from all three observing seasons (61%). In addition, the colors of objects in the variability list and those of the previously cataloged quasars are studied as a possible means of increasing the efficiency of future spectroscopic observing campaigns.