A roadmap to cosmological parameter analysis with third-order shear statistics I: Modelling and validation

TL;DR

This paper develops and validates models for third-order cosmic shear statistics, demonstrating their effectiveness in improving cosmological parameter constraints using simulated data.

Contribution

It introduces a modeling and validation pipeline for third-order shear statistics, enhancing cosmological analysis beyond traditional second-order methods.

Findings

Joint third-order analysis nearly doubles the constraint on S_8.

Third-order statistics increase the figure-of-merit in the Omega_m–sigma_8 plane by 5.9 times.

The modeling pipeline is publicly available for community use.

Abstract

In this work, which is the first of a series to prepare a cosmological parameter analysis with third-order cosmic shear statistics, we model both the shear three-point correlation functions $\Gamma^{(i)}$ and the third-order aperture statistics $\langle\mathcal{M}_\mathrm{ap}^3\rangle$ from the BiHalofit bispectrum model and validate these statistics with a series of N-body simulations. We then investigate how to bin the shear three-point correlation functions to achieve an unbiased estimate for third-order aperture statistics in real data. Finally, we perform a cosmological parameter analysis on KiDS1000-like mock data with second- and third-order statistics. We recover all cosmological parameters with very little bias. Furthermore, we find that a joint analysis almost doubles the constraining power on $S_8$ and increases the figure-of-merit in the $\Omega_\mathrm{m}$-$\sigma_8$ plane by a factor of 5.9 with respect to an analysis with only second-order shear statistics. Our modelling pipeline is publicly available at https://github.com/sheydenreich/threepoint/releases/.