Minimizing the impact of scale-dependent galaxy bias on the joint cosmological analysis of large-scale structures

We present a mitigation strategy to reduce the impact of non-linear galaxy bias on the joint '3 x 2pt' cosmological analysis of weak lensing and galaxy surveys. The Psi-statistics that we adopt are based on Complete Orthogonal Sets of E/B Integrals. As such they are designed to minimize the contributions to the observable from the smallest physical scales where models are highly uncertain. We demonstrate that Psi-statistics carry the same constraining power as the standard two-point galaxy clustering and galaxy-galaxy lensing statistics, but are significantly less sensitive to scale-dependent galaxy bias. Using two galaxy bias models, motivated by halo model fits to data and simulations, we quantify the error in a standard 3 x 2pt analysis where constant galaxy bias is assumed. Even when adopting conservative angular scale cuts, that degrade the overall cosmological parameter constraints, we find of order 1 sigma biases for Stage III surveys on the cosmological parameter S-8 = sigma(8)(Omega(m)/0.3)(alpha). This arises from a leakage of the smallest physical scales to all angular scales in the standard two-point correlation functions. In contrast, when analysing Psi-statistics under the same approximation of constant galaxy bias, we show that the bias on the recovered value for S-8 can be decreased by a factor of similar to 2, with less conservative scale cuts. Given the challenges in determining accurate galaxy bias models in the highly non-linear regime, we argue that 3 x 2pt analyses should move towards new statistics that are less sensitive to the smallest physical scales.

Automated summary

The study introduces a mitigation strategy to reduce the impact of non-linear galaxy bias on the joint cosmological analysis of weak lensing and galaxy surveys, utilizing Psi-statistic to minimize contributions from smallest physical scales and showing comparable constraining power to standard two-point galaxy clustering statistics. It demonstrates a significant decrease in bias on cosmological parameter S-8 when analyzing Psi-statistics compared to standard two-point correlation functions, highlighting the importance of moving towards new statistics less sensitive to smallest physical scales in 3 x 2pt analyses.