HEP-ASTRO SEMINAR | From Giant Arcs to Cosmic Shear: Gravitational Lensing in the Era of Surveys, Speaker: Sanghamitra Deb, Ph.D. (Argonne National Laboratory)
Friday, April 20, 2012
335 West Hall
Speaker: Sanghamitra Deb, Ph.D. (Argonne National Laboratory)The coming decade is going to be very exciting for gravitational lensing science with large surveys like the Dark Energy Survey (DES), the Subaru Hyper-suprime Cam (HSC) , the Large Synaptic Survey Telescope (LSST) and the space based Euclid mission returning data with unprecedented precision. Lensing directly probes the distribution of matter through the bending of light due to gravity. Massive galaxy clusters produce lensing of background sources on all scales ranging from weak lensing on the outskirts to giant arcs and multiple images near their cores. The network of large scale structure in the universe also causes weak lensing of galaxies coherent over cosmological scales; this cosmic shear signal is a sensitive probe of the growth of structure and the evolution of dark energy. In the first part of my talk I will highlight an ongoing cluster lensing study involving a sample of 20 supermassive clusters where we are using the information from shear, magnification and strong lensing to calibrate the normalization and scatter in the mass-temperature relationship of clusters. Such a calibration will be a valuable input to deriving cosmological constraints from cluster number counts. The techniques developed here can be easily extended to optical clusters selected from DES. In the second part of the talk, I will emphasize the need for precision theoretical predictions of the cosmic shear power spectrum on nonlinear scales to fully enable surveys like DES, HSC and LSST to constrain dark energy. I will describe our approach based on the Coyote Universe Emulator that has been shown to predict the three dimensional matter power spectrum to percent level accuracy down to the non-linear scales relevant for lensing.