Peter Andrews

Quasars are among the brightest and most distant objects known, making them intrinsically interesting as well as ideal probes of the history of the universe. Over 23,000 quasars have been found since their discovery four decades ago, but most were identified by various redshift-limited ultraviolet excess methods which excluded extended sources. This prohibits the use of the global quasar sample in a statistical manner for quasar lensing studies.

To improve on this situation, the QUEST survey was born, with the goal of finding large numbers of quasars and gravitational lenses using a uniform selection method for cosmology studies. To date, we have completed three years of driftscan imaging observations using the QUEST 16 CCD camera on the 1m Schmidt telescope at Llano del Hato in Venezuela. Presented here are descriptions of the equipment, data, software and selection methods used, our discovered quasar candidates, a list of confirmed quasars, measured quasar surface densities and comparisons with published results.

Ten nights of UBUV filter data covering 155 square degrees are analyzed using the traditional UV-excess color-selection method to find low-redshift quasars. From the candidates where we obtained spectroscopy, we measured a low-redshift quasar surface density of 5 +/- 1 per square degree to a B magnitude limit of 19.4.
Twenty-five nights of RBRV data taken over three years and covering 250 square degrees are analyzed to find quasars by their variability. To our knowledge the variability portion of our survey is the largest of its kind, using over a dozen nights fully covering most of the huge survey area. Because variability can be used to find quasars uniformly over all redshifts and extended or close groupings of objects are properly treated by our survey, the results here may be less biased with respect to lensed quasars than other selection methods. From the variability candidates where we obtained spectroscopy, we measured a quasar surface density of 42 +/- 10 per square degree to an R magnitude limit of 20.3.