Magnification as a tool in weak lensing

Weak lensing surveys exploit measurements of galaxy ellipticities. These measurements are subject to errors, which degrade the cosmological information that can be extracted from the surveys. Here, we propose a way of using the galaxy data themselves to calibrate the measurement errors. In particular, the cosmic shear field, which causes the galaxies to appear elliptical, also changes their sizes and fluxes. Information about the sizes and fluxes of the galaxies can be added to the shape information to obtain more robust information about the cosmic shear field. The net result will be tighter constraints on cosmological parameters such as those which describe dark energy.