Towards a Bias-Free Selection Function in Shear Measurement

TL;DR

This paper investigates the bias introduced by sample selection in weak lensing shear measurements and proposes a new, low-bias selection function based on the galaxy image power spectrum, suitable for Fourier-based pipelines.

Contribution

It introduces a novel selection function defined in the galaxy image power spectrum that reduces bias in shear measurements.

Findings

The new selection function exhibits lower bias compared to traditional methods.

Simulation results confirm the effectiveness of the proposed selection function.

The method is compatible with Fourier-based shear measurement pipelines.

Abstract

Sample selection is a necessary preparation for weak lensing measurement. It is well-known that selection itself may introduce bias in the measured shear signal. Using image simulation and the Fourier_Quad shear measurement pipeline, we quantify the selection bias in various commonly used selection function (signal-to-noise-ratio, magnitude, etc.). We proposed a new selection function defined in the power spectrum of the galaxy image. This new selection function has low selection bias, and it is particularly convenient for shear measurement pipelines based on Fourier transformation.