Credit: © NASA, ESA, J. Rigby (NASA Goddard Space Flight Center), K. Sharon (Kavli Institute for Cosmological Physics, University of Chicago), and M. Gladders and E. Wuyts (University of Chicago)
Relevant Papers
Gravitational Lensing
As light from distant luminous sources travels through the Universe it gets deflected by the gravitational pull of intervening matter. Light rays from an extended source like a galaxy get deflected in a similar manner with residual deviations conspiring to distort the image of the galaxy. This distortion can be quite dramatic, as in the picture on the right where the strong gravitational field of a massive cluster of galaxies has warped the light from a distant background galaxy into a giant arc-shape. Typically the distortion is weak however, but can be measured statistically in large samples of galaxies by looking for coherent distortions in their shapes. We can also look for small coherent distortions in the cosmic microwave background. In both cases this method allows us to indirectly infer the present of large-scale structure in the distant Universe, and is an incredible powerful technique for studying the way in which matter collapses under gravity in our expanding Universe.
Lensing is a particularly powerful probe of cosmic acceleration, the unexplained observation that our Universe is accelerating in its expansion. It is thought that this behaviour is caused by a mysterious form of energy called ‘dark energy’ making up the bulk of the energy density of the Universe. Lensing can also tell us about the gravitational effects of dark matter, another major constituent of the Universe whose nature is also unknown.
I am particularly interested in weak lensing of galaxies and the CMB, and how best to make use of lensing information to constrain cosmological models. I use a range of mathematical and statistical methods for this purpose, with a particular focus on exploring synergies between different branches of cosmology in the context of weak lensing. I am a member of the Euclid Consortium, a European Space Agency Space Telescope due for launch in mid-2022. This satellite will conduct a weak lensing survey over a large portion of the sky and will help us to understand the nature of dark matter and dark energy. We also aim to measure the mass of the neutrino with this telescope — such a measurement would have huge implications for fundamental particle physics.