Weak Lensing By Nearby Structures

TL;DR

This paper discusses how weak gravitational lensing by nearby structures can polarize distant galaxy images, and how upcoming surveys could measure this effect to determine local matter density parameter Omega.

Contribution

It proposes using polarization measurements from weak lensing to estimate the local matter density parameter Omega, offering a novel observational approach.

Findings

Polarization due to nearby structures is expected to be around 0.2%.

Upcoming surveys can detect polarization levels of about 0.1%.

This method allows comparison of local Omega with other techniques.

Abstract

Weak gravitational lensing due to nearby structures, such as the Coma cluster, and the Local Supercluster can be expected to polarize images of distant galaxies by ${\cal O}(0.2%\Omega)$ with coherence over scales of tens of square degrees. The Sloan Survey, which will image $\gsim 10^4$ galaxies $\rm deg^{-2}$ over $\pi$ steradians, should be sensitive to polarizations of $\sim 0.1% A^{-1/2}$, where $A$ is the area in square degrees. By measuring the polarization, one could determine $\Omega$ in local structures and compare this value to that derived from a variety of other techniques.