ar X iv : a st ro - p h / 96 12 03 1 v 1 3 D ec 1 99 6 Faint galaxies around quasars at z = 1 and gravitational lensing of distant objects

Received ; accepted – 2 – ABSTRACT Very deep imaging data of three optically luminous radio-loud quasars with redshifts between z = 0.9 and z = 1.36 are presented. The data are complete for galaxies down to R = 26. There is no evidence for excess numbers of galaxies around the quasars; foreground galaxy clusters are excluded by the data as well as clusters with richness classes greater than 1 associated with the quasars. We find clear evidence for gravitational lensing for two quasars. It is further shown that due to the high surface density of galaxies all distant (z > 1) objects are moderately affected by gravitational lensing; the amplification factors are estimated to be in the range 1.1 − 1.5. Subject headings: Quasars – environment of quasars – gravitational lensing-galaxy halos – 3 –