Impact of cosmology dependence of baryonic feedback in weak lensing

TL;DR

This paper investigates how the interaction between baryonic feedback and cosmology affects weak lensing parameter inference, highlighting the robustness of PCA and potential biases in HMCode2020.

Contribution

It demonstrates the importance of modeling the cosmology dependence of baryonic feedback and compares two mitigation techniques using hydrodynamical simulations.

Findings

PCA method is robust to feedback-cosmology coupling.

HMCode2020 can introduce up to 0.5σ bias in parameters.

Bias in HMCode2020 correlates with input cosmology.

Abstract

Robust modeling of non-linear scales is critical for accurate cosmological inference in Stage IV surveys. For weak lensing analyses in particular, a key challenge arises from the incomplete understanding of how non-gravitational processes, such as supernovae and active galactic nuclei - collectively known as baryonic feedback - affect the matter distribution. Several existing methods for modeling baryonic feedback treat it independently from the underlying cosmology, an assumption which has been found to be inaccurate by hydrodynamical simulations. In this work, we examine the impact of this coupling between baryonic feedback and cosmology on parameter inference at LSST Y1 precision. We build mock 3$\times$2pt data vectors using the Magneticum suite of hydrodynamical simulations, which span a wide range of cosmologies while keeping subgrid parameters fixed. We perform simulated likelihood analyses for two baryon mitigation techniques: (i) the Principal Component Analysis (PCA) method which identifies eigenmodes for capturing the effect baryonic feedback on the data vector and (ii) HMCode2020 (Mead et al. 2021) which analytically models the modification in the matter distribution using a halo model approach. Our results show that the PCA method is robust to the coupling between cosmology and baryonic feedback, whereas, when using HMCode2020 there can be up to $0.5\sigma$ bias in $\Omega_\text{m}$-$S_8$. For HMCode2020, the bias also correlates with the input cosmology while for PCA we find no such correlation.