Measuring cosmic shear with the ring statistics

TL;DR

The paper introduces improvements to the ring statistics method for cosmic shear analysis, demonstrating its effectiveness in decomposing E- and B-modes, constraining cosmology, and measuring signals from CFHTLS data, with advantages in systematic identification.

Contribution

It enhances the ring statistics' filter function for better signal-to-noise, compares its cosmological constraints to other methods, and applies it to real CFHTLS data for cosmic shear measurement.

Findings

Improved filter function increases signal-to-noise ratio.

Ring statistics effectively constrains cosmological parameters.

Application to CFHTLS data successfully measures cosmic shear.

Abstract

Commonly used methods to decompose E- and B-modes in cosmic shear, namely the aperture mass dispersion and the E/B-mode shear correlation function, suffer from incomplete knowledge of the two-point correlation function (2PCF) on very small and/or very large scales. The ring statistics, the most recently developed cosmic shear measure, improves on this issue and is able to decompose E- and B-modes using a 2PCF measured on a finite interval. First, we improve on the ring statistics' filter function with respect to the signal-to-noise ratio. Second, we examine the ability of the ring statistics to constrain cosmology and compare the results to cosmological constraints obtained with the aperture mass dispersion. Third, we use the ring statistics to measure a cosmic shear signal from CFHTLS (Canada-France-Hawaii Telescope Legacy Survey) data. We consider a scale-dependent filter function for the ring statistics which improves its signal-to-noise ratio. In addition, we show that there exist filter functions which decompose E- and B-modes using a finite range of 2PCFs (EB-statistics) and have higher S/N ratio than the ring statistics. However, we find that data points of the latter are significantly less correlated than data points of the aperture mass dispersion and the EB-statistics. As a consequence the ring statistics is an ideal tool to identify remaining systematics accurately as a function of angular scale. We use the 2PCF of the latest CFHTLS analysis and therefrom calculate the ring statistics and its error bars.