Complementarity of Weak Lensing and Peculiar Velocity Measurements in Testing General Relativity

TL;DR

This paper investigates how combining weak lensing and peculiar velocity data can improve constraints on modifications to General Relativity, showing no current deviations but promising future precision improvements.

Contribution

It introduces a combined analysis approach for lensing and velocity data, forecasts future constraints with Euclid-like surveys, and presents a model-independent method for testing gravity.

Findings

No evidence for deviations from GR in current data.

Future surveys can constrain modified gravity to 5% accuracy.

A new tomographic velocity method for gravity tests is proposed.

Abstract

We explore the complementarity of weak lensing and galaxy peculiar velocity measurements to better constrain modifications to General Relativity. We find no evidence for deviations from GR on cosmological scales from a combination of peculiar velocity measurements (for Luminous Red Galaxies in the Sloan Digital Sky Survey) with weak lensing measurements (from the CFHT Legacy Survey). We provide a Fisher error forecast for a Euclid-like space-based survey including both lensing and peculiar velocity measurements, and show that the expected constraints on modified gravity will be at least an order of magnitude better than with present data, i.e. we will obtain 5% errors on the modified gravity parametrization described here. We also present a model--independent method for constraining modified gravity parameters using tomographic peculiar velocity information, and apply this methodology to the present dataset.