Speaker: Alan Heavens (Imperial College London)

Title: Weak lensing with uncertain redshifts

Abstract:  
The cosmological conclusions of weak lensing surveys are very sensitive to the assumed redshift distributions of sources placed in different tomographic bins. In reality, these distributions are not known quantities, so from a Bayesian perspective they should be treated as random objects, constrained by data. For photometric redshifts, the data are fluxes in a number of bands, and the usual approach is to infer the redshift distributions from the inferred redshifts of individual sources. However, that is a far from trivial task, so it is better to infer the redshift distributions directly. In this talk, using the work of student George Kyriacou, we look at the influence of this redshift uncertainty (from a principled Bayesian perspective) on the tension in the strength of clustering between the KiDS-Viking 450 cosmic shear survey and the Planck.