Shear and magnification: cosmic complementarity

The potential of cosmic shear to probe cosmology is well recognized and future optical wide field surveys are currently being designed to optimize the return of cosmic shear science. High precision cosmic shear analysis requires high precision photometric redshift. With accurate photometric redshifts, it becomes possible to measure the cosmic magnification on galaxies by galaxies and use it as a probe of cosmology. This type of weak lensing measurement will not use galaxy shapes, instead it will strongly rely on precise photometry and detailed colour information. In this work it is shown that such a measurement would lead to competitive constraints of the cosmological parameters, with a remarkable complementarity with cosmic shear. Future cosmic shear surveys could gain tremendously from magnification measurements as an independent probe of the dark matter distribution leading to a better control of observational and theoretical systematics when combined with shear.

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