Marshak Lectureship: Cosmological constraints from the Subaru Hyper Suprime-Cam Survey first year data

How does dark energy affect the growth of cosmic structure? The Hyper Suprime-Cam Survey conducted from the Subaru telescope is a 1400 square degree imaging survey of the sky which aims to answer this question. The wide field of view of Subaru, the unprecedented survey depth, combined with the excellent imaging quality, makes it ideal to study the shapes of millions of galaxies in a large part of the sky. Gravitational lensing, the bending of light due to gravity, induces tiny distortions in the shapes of these galaxies. These tiny distortions together reveal the matter distribution and can be used to measure the growth of cosmic structure. I will report on the cosmology results from the first year of the HSC survey covering 140 square degrees on the sky. We measure and model the cosmic shear power spectrum and constrain the amplitude of density fluctuations in the Universe today. Although our results are consistent with the fluctuations evolved from the cosmic microwave background observations of the Planck satellite, all cosmic shear surveys, including ours, show tantalizing hints of the growth of structure being slower than expected from the concordance cosmological model. I will discuss the implications and the future prospects of confirming or ruling out these deviations.