Cosmic Shear Measurement using Autoconvolved Images

TL;DR

This paper introduces a novel method for measuring cosmic shear using quadrupole moments of auto-convolved galaxy images, which simplifies PSF correction and noise removal, achieving sub-percent accuracy in simulations.

Contribution

The paper presents a new technique utilizing auto-convolved images for cosmic shear measurement, improving PSF correction and noise handling over previous methods.

Findings

Achieves sub-percent accuracy in simulated conditions.

Effectively corrects PSF smearing effects.

Removes noise systematic errors directly in Fourier space.

Abstract

We study the possibility of using quadrupole moments of auto-convolved galaxy images to measure cosmic shear. The autoconvolution of an image corresponds to the inverse Fourier transformation of its power spectrum. The new method has the following advantages: the smearing effect due to the Point Spread Function (PSF) can be corrected by subtracting the quadrupole moments of the auto-convolved PSF; the centroid of the auto-convolved image is trivially identified; the systematic error due to noise can be directly removed in Fourier space; the PSF image can also contain noise, the effect of which can be similarly removed. With a large ensemble of simulated galaxy images, we show that the new method can reach a sub-percent level accuracy in general conditions, albeit with increasingly large stamp size for galaxies of less compact profiles.