ANGULAR CROSS-CORRELATION OF GALAXIES - A PROBE OF GRAVITATIONAL LENSING BY LARGE-SCALE STRUCTURE

The angular cross-correlation between two galaxy samples separated in redshift is shown to be a useful measure of weak lensing by large-scal e structure. Angular correlations in faint galaxies arise as a result of spatial clustering of the galaxies as well as gravitational lensing by dark matter along the line of sight. The lensing contribution to t he two-point autocorrelation function is typically small compared with the gravitational clustering. However, the cross-correlation between two galaxy samples is almost unaffected by gravitational clustering pr ovided that their redshift distributions do not overlap. The cross-cor relation is then induced by magnification bias resulting from lensing by large-scale structure. We compute the expected amplitude of the cro ss-correlation for popular theoretical models of structure formation. For two populations. with mean redshifts of similar or equal to 0.3 an d 1, we find a crosscorrelation signal of similar or equal to 1 per ce nt on arcmin scales and similar or equal to 3 per cent on scales of a few arcsec. The dependence on the cosmological parameters Omega and La mbda, the dark matter power spectrum and the bias factor of the foregr ound galaxy population is explored.