J. Surdej et al., GRAVITATIONAL LENSING STATISTICS BASED ON A LARGE-SAMPLE OF HIGHLY LUMINOUS QUASARS, The Astronomical journal, 105(6), 1993, pp. 2064-2078
Results on gravitational lensing statistics applied to a sample of 469
highly luminous quasars are reported. The objects were directly image
d, either from the ground (ESO, CFH) under optimal seeing conditions,
or using the Hubble Space Telescope. We have derived values for the ef
fectiveness parameter F of galaxies, modeled by means of singular isot
hermal spheres, to produce macrolensed images of distant quasars, and
upper limits on the density parameter OMEGA(L) of compact objects with
masses congruent-to 10(10)-10(12)M .. Adopting H0=50 km/s/Mpc, OMEGA0
=1 and LAMBDA=0, we find that at the 99.7% confidence level, 0.005 < F
< 0.478 and that OMEGA(L) < 0.02. A critical discussion of these resu
lts is presented. Finally, comparing the efficiencies of ground-based
and space instruments used to search for gravitational lens systems am
ong highly luminous quasars, we conclude that for the near future, gro
und based direct imaging characterized by a good dynamical range still
constitutes the best observational strategy.