Seminaire Lagrange -- Pierre Fleury (LUMP-Montpellier) -- Cosmic shear with Einstein rings

Pierre Fleury (LUMP-Montpellier) 

Cosmic shear with Einstein rings

An Einstein ring is an image formed by strong gravitational lensing, when a massive galaxy (the lens) lies on the line of sight of another, more distant, background galaxy (the source). Such images are traditionally modelled as if the lens were alone in an otherwise homogeneous Universe. In reality, however, all the inhomogeneities along the line of sight also contribute to the deflection of light and thereby imprint perturbations to the Einstein ring. This offers a fantastic opportunity to probe cosmic shear with Einstein rings. I will explain how this works, expose a proof of concept, and elaborate on perspectives for the Euclid survey.