Cosmological information from quasar-galaxy correlations induced by weak lensing

¹ Max-Planck-Institut für Astrophysik, PO Box 1317, 85741 Garching, Germany
² Institut d'Astrophysique de Paris, 98bis Bld. Arago, 75014 Paris, France

Corresponding author: B. Ménard, menard@mpa-garching.mpg.de

Received: 4 December 2001
Accepted: 14 February 2002

Abstract

The magnification bias of large-scale structures, combined with galaxy biasing, leads to a cross-correlation of distant quasars with foreground galaxies on angular scales of the order of arcminutes and larger. The amplitude and angular shape of the cross-correlation function w_QG contain information on cosmological parameters and the galaxy bias factor. While the existence of this cross-correlation has firmly been established, existing data did not allow an accurate measurement of w_QG yet, but wide area surveys like the Sloan Digital Sky Survey now provide an ideal database for measuring it. However, w_QG depends on several cosmological parameters and the galaxy bias factor. We study in detail the sensitivity of w_QG to these parameters and develop a strategy for using the data. We show that the parameter space can be reduced to the bias factor , and , and compute the accuracy with which these parameters can be deduced from SDSS data. Under reasonable assumptions, it should be possible to reach relative accuracies of the order of – for , , and . This method is complementary to other weak-lensing analyses based on cosmic shear.