Effect of Our Galaxy's Motion on Weak Lensing Measurements of Shear and Convergence

TL;DR

This paper studies how the motion of our Galaxy causes magnification effects that influence weak lensing measurements of shear and convergence, especially for large sky surveys, highlighting the importance of accounting for these distortions.

Contribution

It quantifies the impact of the Galaxy's Lorentz boost on weak lensing measurements, emphasizing effects on convergence and large-scale surveys, and clarifies when this effect can be neglected.

Findings

Galaxy's motion causes a 10% magnification effect on convergence.

The boost effect significantly impacts low multipoles in the convergence power spectrum.

Small sky surveys and high multipole measurements can ignore the boost effect to first order.

Abstract

In this work we investigate the effect on weak-lensing shear and convergence measurements due to distortions from the Lorentz boost induced by our Galaxy's motion. While no ellipticity is induced in an image from the Lorentz boost to first order in beta = v/c, the image is magnified. This affects the inferred convergence at a 10 per cent level, and is most notable for low multipoles in the convergence power spectrum C {\kappa}{\kappa} and for surveys with large sky coverage like LSST and DES. Experiments which image only small fractions of the sky and convergence power spectrum determinations at l > 5 can safely neglect the boost effect to first order in beta.