Measuring Omega_0 with higherorder QuasarGalaxy Correlations induced by Weak Lensing
Abstract
Via the magnification bias, gravitational lensing by largescale structures causes angular crosscorrelations between distant quasars and foreground galaxies on angular scales of arc minutes and above. We investigate the threepoint crosscorrelation 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 arc minute. Combining two and threepoint correlations, a skewness parameter can be defined which is shown to be virtually independent on the shape and normalisation of the darkmatter power spectrum. If the galaxy bias is linear and deterministic, the skewness depends on the cosmic matter density parameter Omega_0 only; otherwise, it can be used to probe the linearity and stochasticity of the bias. We finally estimate the signaltonoise ratio of a skewness determination and find that around twenty thousand distant quasars e.g. from the Sloan Digital Sky Survey should suffice for a direct measurement of Omega_0.
 Publication:

arXiv eprints
 Pub Date:
 August 2002
 arXiv:
 arXiv:astroph/0208361
 Bibcode:
 2002astro.ph..8361M
 Keywords:

 Astrophysics
 EPrint:
 11 pages, 6 figures, submitted to Astronomy and Astrophysics