P3	March 1997

¹ Institut d'Astrophysique et de Géophysique - Université de Liège, Avenue de Cointe 5, 4000 Liège, Belgium

^* Directeur de Recherches FNRS, Belgium
^** Aspirant FNRS, Belgium

Abstract

     Given the very small number (~25) of known multiply imaged quasars, almost randomly distributed over the sky, the probability to observe even only one of these within the ~30' zenithal field of view of a Liquid Mirror Telescope (LMT) is virtually zero. Therefore, the observational stategy for studies of gravitational lensing effects with a LMT rather consists in first surveying a sky area as deep and as wide as possible for interesting targets (cf. quasar candidates using color or variability criteria) and then select gravitational lens candidates among them. The extend of the field of view is of course primarily dictated by the number and/or the size of the thin CCDs placed at the LMT prime focus. For the case of multiply imaged quasars, we find that direct imagery with a 4m LMT would lead, after less than six weeks of effective operation, to the detection of approximately 50 new gravitational lens systems (₀ = 1, ₀ = 0). The natural possibility to photometrically monitor these at daily intervals offers a unique opportunity to define a sub-sample of interesting lenses with reliable geometrical parameters, time delay measurements and/or micro-lensing signatures for further astrophysical and cosmological applications. For several obvious reasons (acces to the south galactic pole, galactic center, good image quality, ...), a best site location for such a LMT is somewhere in the Atacama desert. At the latitude near -29.5 degrees, a deep LMT survey would cover ~90 square degrees at high galactic latitude, specially useful for the GL studies proposed here, for the identification of various classes of interesting extragalactic objects (cf. galaxies, clusters, supernovae, etc. at high redshift) and subsequent follow-up observations with the VLT. Such a survey would in addition provide unique data for studies of the galactic structure and stellar populations, including the detection of micro-lensed galactic objects, accurate measurements of stellar proper motions useful for the detection of faint red, white and brown dwarfs, halo stars, etc.