A search for gravitational lensing among highly luminous quasars - New results

Images of highly luminous QSOs are analyzed to determine whether the gravitational magnification of the background QSO by matter associated with the foreground galaxies accounts for the excess of galaxies in the fields of distant QSOs. Galaxy detection is increased by utilizing red-filter images, 40 taken with the EFOSC at the ESO 3.6-m telescope and 43 taken with a direct CCD camera at the ESO/MPI 2.2-m telescope. The R-magnitude ranges from 22.5 to 23.0 for the sample, for which the number of galaxies is counted by eye, showing 45 galaxies of radio and optical type. The overdensity found is not as pronounced as that of Fugmann (1988) or that of Webster et al. (1988). A systematic subtraction of the point spread function is also described to investigate the idea that some galaxies responsible for the QSO light magnification are within the inner 3-arcsec circle. The galaxies very close to the line-of-sight are theorized to contribute significantly to the magnification of these QSOs.