# On Weak Lensing Shape Noise

**Authors:** Sami-Matias Niemi, Thomas Kitching, Mark Cropper  
**arXiv:** [1509.05058](https://arxiv.org/abs/1509.05058)  
**Date:** 2015-09-16  
**Summary page:** https://www.summarizepaper.com/en/paper/1509.05058v1/

## Key points

- Weak gravitational lensing is a powerful technique for studying the dark sector of the Universe
- Galaxy shapes measured through weak lensing are affected by intrinsic ellipticity and integrated gravitational lensing effect, resulting in shape noise that reduces the power of weak lensing surveys
- Authors have developed a general method for extracting probability distributions from data catalogues using Voronoi cells to reduce shape noise significantly
- The team applied their method to CFHTLenS survey data and used it to investigate trends in galaxy properties, as well as weak lensing power spectra analysis
- Reducing shape noise could lead to significant advances in the power of weak lensing surveys and improve our ability to measure cosmic shear accurately.

## Summary

The study of the dark sector of the Universe is a challenging task, but one of the most powerful techniques to achieve this is through weak gravitational lensing. To infer the reduced shear, weak lensing measures galaxy shapes which are affected by both intrinsic ellipticity and integrated gravitational lensing effect along the line of sight. This results in a significant amount of `shape noise', which can reduce the power of weak lensing surveys. To overcome this challenge, authors Sami-Matias Niemi, Thomas Kitching, and Mark Cropper have developed a general method for extracting probability distributions from catalogues of data using Voronoi cells. The approach has several applications and synergies with Bayesian hierarchical modelling approaches. By constructing a probability distribution for the variance of intrinsic ellipticity as a function of galaxy property using only photometric data, it is possible to reduce shape noise significantly. As proof-of-concept, the team applied their method to CFHTLenS survey data and used it to investigate trends in galaxy properties. They also applied it to weak lensing power spectra analysis. The results showed that reducing shape noise could lead to significant advances in the power of weak lensing surveys. Overall, this research provides an innovative solution for reducing shape noise in weak gravitational lensing surveys by extracting probability distributions from catalogues using Voronoi cells. It opens up new avenues for studying dark matter and other aspects related to cosmology by improving our ability to measure cosmic shear accurately.