Weak Lensing Measurements in Simulations of Radio Images

TL;DR

This paper develops a simulation pipeline for radio galaxy images to evaluate weak lensing shear measurement techniques, demonstrating accurate ellipticity recovery with minimal bias, aiding future radio telescope surveys.

Contribution

It introduces a comprehensive simulation pipeline for radio weak lensing, including realistic effects and testing shear measurement methods, which is novel for radio weak lensing studies.

Findings

Ellipticities can be measured accurately with minimal bias.

The pipeline effectively models realistic radio observation effects.

Shear measurement methods are validated for future radio surveys.

Abstract

We present a study of weak lensing shear measurements for simulated galaxy images at radio wavelengths. We construct a simulation pipeline into which we can input galaxy images of known ellipticity, and with which we then simulate observations with eMERLIN and the international LOFAR array. The simulations include the effects of the CLEAN algorithm, uv sampling, observing angle, and visibility noise, and produce realistic restored images of the galaxies. We apply a shapelet-based shear measurement method to these images and test our ability to recover the true source ellipticities. We model and deconvolve the effective PSF, and find suitable parameters for CLEAN and shapelet decomposition of galaxies. We demonstrate that ellipticities can be measured faithfully in these radio simulations, with no evidence of an additive bias and a modest (10%) multiplicative bias on the ellipticity measurements. Our simulation pipeline can be used to test shear measurement procedures and systematics for the next generation of radio telescopes.