Deep lensing with a twist: E and B modes in a field with multiple lenses

TL;DR

This paper investigates the weak lensing E- and B-mode signals in a galaxy cluster field using simulations and observations, developing a model to relate B-modes to foreground structures and identifying key sources of B-mode contamination.

Contribution

It introduces a novel method to model foreground structures as superpositions of NFW-like halos and links B-mode signals to these models, advancing understanding of B-mode origins in cosmic shear.

Findings

B-mode maps agree with observations and relate to cluster properties.

Identified sources of B-modes include leakage, edge effects, source clustering, and multiple lensing.

Foreground mass modeling helps interpret B-mode signals in deep surveys.

Abstract

We explore the weak lensing E- and B-mode shear signals of a field of galaxy clusters using both large scale structure N-body simulations and multi-color Suprime-cam & Hubble Space Telescope observations. Using the ray-traced and observed shears along with photometric redshift catalogs, we generate mass maps of the foreground overdensities by optimally filtering the tangential shear that they induce on background galaxies. We then develop and test a method to approximate the foreground structure as a superposition of NFW-like halos by locating these overdensities and determining their mass and redshift, thereby modeling the background correlated shear field as a sum of lensings induced by the foreground clusters. We demonstrate that the B-mode maps and shear correlation functions, which are generated by similarly filtering the cross shear in this method, are in agreement with observations and are related to the estimated cluster masses and locations as well as the distribution of background sources. Using the foreground mass model, we identify several sources of weak lensing B-modes including leakage and edge effects, source clustering, and multiple lensing which can be observed in deep cosmic shear surveys.