Volume 409, Number 2, October II 2003
|Page(s)||411 - 421|
|Section||Cosmology (including clusters of galaxies)|
|Published online||17 November 2003|
Measuring with higher-order quasar-galaxy correlations induced by weak lensing
Max-Planck-Institut für Astrophysik, PO Box 1317, 85741 Garching, Germany
2 Institut d'Astrophysique de Paris, 98bis Bld. Arago, 75014 Paris, France
3 LERMA, Observatoire de Paris, 61 avenue de l'Observatoire, 75014 Paris, France
Corresponding author: B. Ménard, firstname.lastname@example.org
Accepted: 20 May 2003
Via the magnification bias, gravitational lensing by large-scale structures causes angular cross-correlations between distant quasars and foreground galaxies on angular scales of arcminutes and above. We investigate the three-point cross-correlation between quasars and galaxy pairs measurable via the second moment of the galaxy counts around quasars and show that it reaches the level of a few per cent on angular scales near one arcminute. Combining two- and three-point correlations, a skewness parameter can be defined which is shown to be virtually independent of the shape and normalisation of the dark-matter power spectrum. If the galaxy bias is linear and deterministic, the skewness depends on the cosmic matter density parameter only; otherwise, it can be used to probe the non-linearity and stochasticity of the bias. We finally estimate the signal-to-noise ratio of a skewness determination and find that a sample of about twenty thousand distant quasars e.g. from the Sloan Digital Sky Survey should suffice for a direct measurement of .
Key words: cosmology: gravitational lensing / cosmology: large-scale structure of Universe
© ESO, 2003
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