Cosmological Tests with Weak Gravitational Lensing Surveys

University Of Pennsylvania, Philadelphia PA

Investigators

Abstract

Dr Bernstein, Dr Jain and their team will develop and test software to extract information on weak gravitational lensing from large imaging surveys. Weak lensing refers to the small distortions in the images of distant galaxies that result when its light is bent by the gravitational pull of clumps of matter that lie along the light path. This work therefore gives information about how mass is distributed on the largest cosmic scales. The team will explore better techniques for measuring the shapes of galaxy images. They will improve the performance of pipeline software for determining the point spread function (PSF, which measures the distorting effect of the Earth's atmosphere and the telescope optics on the images), and for measuring galaxy colors, and the distances inferred from those colors, even when the PSF differs between images in different colors. They will develop a method to find the combination of cosmological parameters that best fits a given set of such observations, while taking account of important systematic errors, and making use of all the available information in the survey images, but remaining computationally feasible. Finally, the team will explore the best combination of lensing measurements to test theories of modified gravity, which have been proposed as alternatives to dark energy in explaining the observed cosmic acceleration. The software developed will be tested with commissioning data from the Dark Energy Survey prior to the start of the main survey. Two graduate students will be trained as they participate in the research. The proposed improvements in measurements of galaxy shape, color and estimated distances will be generally applicable to astronomical imaging surveys, and should be useful for studies beyond gravitational lensing.