Optimizing weak lensing mass estimates for cluster profile uncertainty

TL;DR

This paper develops an optimized weak lensing mass estimator using N-body simulations to reduce variance caused by cluster profile uncertainties and line-of-sight structures, improving mass calibration accuracy.

Contribution

The authors introduce a new circular aperture mass measurement that minimizes variance from multiple sources of cluster and line-of-sight variability, enhancing weak lensing mass estimates.

Findings

The new estimator reduces variance more effectively than traditional methods.

Optimizing for uncorrelated large-scale structure improves estimates but can be counterproductive if internal cluster variability is ignored.

The method's performance depends on observational conditions and halo mass.

Abstract

Weak lensing measurements of cluster masses are necessary for calibrating mass-observable relations (MORs) to investigate the growth of structure and the properties of dark energy. However, the measured cluster shear signal varies at fixed mass M_200m due to inherent ellipticity of background galaxies, intervening structures along the line of sight, and variations in the cluster structure due to scatter in concentrations, asphericity and substructure. We use N-body simulated halos to derive and evaluate a weak lensing circular aperture mass measurement M_ap that minimizes the mass estimate variance <(M_ap - M_200m)^2> in the presence of all these forms of variability. Depending on halo mass and observational conditions, the resulting mass estimator improves on M_ap filters optimized for circular NFW-profile clusters in the presence of uncorrelated large scale structure (LSS) about as much as the latter improve on an estimator that only minimizes the influence of shape noise. Optimizing for uncorrelated LSS while ignoring the variation of internal cluster structure puts too much weight on the profile near the cores of halos, and under some circumstances can even be worse than not accounting for LSS at all. We briefly discuss the impact of variability in cluster structure and correlated structures on the design and performance of weak lensing surveys intended to calibrate cluster MORs.