Weak Lensing Magnification Reconstruction with the Modified Internal Linear Combination Method

TL;DR

This paper introduces a modified ILC method to reconstruct weak lensing magnification signals, effectively suppressing intrinsic clustering and achieving unbiased results with less than 5% statistical uncertainty for specific photo-z bin widths.

Contribution

The paper develops a modified ILC technique with an additional constraint to improve weak lensing magnification reconstruction accuracy.

Findings

Reconstruction performance varies with photo-z bin width.

Narrower bins reduce systematic bias but increase statistical uncertainty.

Unbiased lensing signal with <5% uncertainty for Δz^P=0.2.

Abstract

Measuring weak lensing cosmic magnification signal is very challenging due to the overwhelming intrinsic clustering in the observed galaxy distribution. In this paper, we modify the Internal Linear Combination (ILC) method to reconstruct the lensing signal with an extra constraint to suppress the intrinsic clustering. To quantify the performance, we construct a realistic galaxy catalogue for the LSST-like photometric survey, covering $20\,000\ \deg^2$ with mean source redshift at $z_s\sim 1$. We find that the reconstruction performance depends on the width of the photo-z bin we choose. Due to the correlation between the lensing signal and the source galaxy distribution, the derived signal has smaller systematic bias but larger statistical uncertainty for a narrower photo-z bin. We conclude that the lensing signal reconstruction with the Modified ILC method is unbiased with a statistical uncertainty $<5\%$ for bin width $\Delta z^P = 0.2$.