QSO-galaxy correlations due to weak lensing in arbitrary Friedmann-Lemaitre cosmologies

Abstract

We calculate the angular cross-correlation function between background QSOs and foreground galaxies induced by the weak lensing effect of large-scale structures. Results are given for arbitrary Friedmann-Lemaitre cosmologies. The non-linear growth of density perturbations is included. Compared to the linear growth, the non-linear growth increases the correlation amplitude by about an order of magnitude in an Einstein-de Sitter universe, and by even more for lower Omega_0. The dependence of the correlation amplitude on the cosmological parameters strongly depends on the normalization of the power spectrum. The QSO-galaxy cross-correlation function is most sensitive to density structures on scales in the range (1-10) Mpc/h, where the normalization of the power spectrum to the observed cluster abundance appears most appropriate. In that case, the correlation strength changes by less than a factor of <~ 2 when Omega_0 varies between 0.3 and 1, quite independent of the value of Omega_Lambda. For Omega_0 <~ 0.3, the correlation strength increases with decreasing Omega_0, and it scales approximately linearly with the Hubble constant h.