Weak Lensing Magnification – A New Window to Cosmology

Hendrik Hildebrandt

November 22, 2010

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Abstract: Weak gravitational lensing (WL) is a unique tool to study the large-scale mass distribution of the universe since it is sensitive to both, visible and dark matter (DM). So far, the large-scale structure has been mainly studied through WL by employing its shear effect. In this talk I will present a new, complementary method based on the magnification effect of WL. We measure the cross-correlation functions of background Lyman-break galaxies (LBGs) selected from the CFHTLS to foreground lenses selected by accurate photo-z’s. The amplitude and shape of the signal depend on cosmology and on the luminosity function of the LBGs, and we show that our measurements agree very well with theoretical expectations. Upcoming measurements on the CFHTLS-Wide data set will yield the first cosmological constraints from WL magnification. Furthermore, we study the magnitude-shift effect of magnification from the same data which will be used to estimate the profiles of the DM- and dust-halos of galaxies out to z~1.