Effects of large-scale structure on the accuracy of weak lensing mass measurements

TL;DR

This paper investigates how large-scale structure along the line of sight impacts the accuracy of weak lensing mass measurements of galaxy clusters, revealing it as a significant source of uncertainty comparable to statistical errors.

Contribution

It demonstrates that line-of-sight large-scale structure significantly affects weak lensing mass estimates and evaluates the limited benefits of modeling this structure to improve precision.

Findings

Large-scale structure contributes significantly to measurement errors.

Analytical calculations are validated using Millennium Simulation data.

Modeling the structure offers only slight improvements in mass measurement accuracy.

Abstract

Weak gravitational lensing has become an important method to determine the masses of galaxy clusters. The intrinsic shapes of the galaxies are a dominant source of uncertainty, but there are other limitations to the precision that can be achieved. In this paper we revisit a typically ignored source of uncertainty: structure along the line-of sight. Using results from the Millennium Simulation we confirm the validity of analytical calculations that have shown that such random projections are particularly important for studies of the cluster density profile. In general the contribution of large-scale structure to the total error budget is comparable to the statistical errors. We find that the precision of the mass measurement can be improved only slightly by modelling the large-scale structure using readily available data.