Cosmic Shear as a Probe of Galaxy Formation Physics

TL;DR

This paper assesses how current and future cosmic shear measurements can constrain baryonic physics effects on the matter power spectrum, highlighting the potential of upcoming surveys to provide insights into galaxy formation.

Contribution

It introduces a model-independent principal component approach to quantify the constraining power of cosmic shear data on baryonic effects across different surveys.

Findings

Future surveys like DES Y5, LSST, Euclid, and WFIRST will significantly improve constraints.

Most constraining information is contained in no more than nine principal components.

Controlling small-scale systematics is crucial for maximizing the power of cosmic shear measurements.

Abstract

We evaluate the potential for current and future cosmic shear measurements from large galaxy surveys to constrain the impact of baryonic physics on the matter power spectrum. We do so using a model-independent parameterization that describes deviations of the matter power spectrum from the dark-matter-only case as a set of principal components that are localized in wavenumber and redshift. We perform forecasts for a variety of current and future datasets, and find that at least ~90% of the constraining power of these datasets is contained in no more than nine principal components. The constraining power of different surveys can be quantified using a figure of merit defined relative to currently available surveys. With this metric, we find that the final Dark Energy Survey dataset (DES Y5) and the Hyper Suprime Cam Survey will be roughly an order of magnitude more powerful than existing data in constraining baryonic effects. Upcoming Stage IV surveys (LSST, Euclid, and WFIRST) will improve upon this by a further factor of a few. We show that this conclusion is robust to marginalization over several key systematics. The ultimate power of cosmic shear to constrain galaxy formation is dependent on understanding systematics in the shear measurements at small (sub-arcminute) scales. If these systematics can be sufficiently controlled, cosmic shear measurements from DES Y5 and other future surveys have the potential to provide a very clean probe of galaxy formation and to strongly constrain a wide range of predictions from modern hydrodynamical simulations.