Simultaneously constraining cosmology and baryonic physics via deep learning from weak lensing

TL;DR

This paper develops a deep learning approach using CNNs to simultaneously constrain cosmological parameters and baryonic physics from weak lensing data, effectively capturing non-Gaussian features and mitigating baryonic uncertainties.

Contribution

It introduces a CNN-based method that jointly constrains cosmology and baryonic effects from weak lensing maps, outperforming traditional power spectrum and peak count analyses.

Findings

CNN achieves 1.7x tighter constraints than power spectrum.

Combining CNN with power spectrum reduces baryonic impact on constraints.

CNN effectively captures non-Gaussian information while marginalizing over baryonic effects.

Abstract

Ongoing and planned weak lensing (WL) surveys are becoming deep enough to contain information on angular scales down to a few arcmin. To fully extract information from these small scales, we must capture non-Gaussian features in the cosmological WL signal while accurately accounting for baryonic effects. In this work, we account for baryonic physics via a baryonic correction model that modifies the matter distribution in dark matter-only $N$-body simulations, mimicking the effects of galaxy formation and feedback. We implement this model in a large suite of ray-tracing simulations, spanning a grid of cosmological models in $\Omega_\mathrm{m}-\sigma_8$ space. We then develop a convolutional neural network (CNN) architecture to learn and constrain cosmological and baryonic parameters simultaneously from the simulated WL convergence maps. We find that in a Hyper-Suprime Cam (HSC)-like survey, our CNN achieves a 1.7$\times$ tighter constraint in $\Omega_\mathrm{m}-\sigma_8$ space ($1\sigma$ area) than the power spectrum and 2.1$\times$ tighter than the peak counts, showing that the CNN can efficiently extract non-Gaussian cosmological information even while marginalizing over baryonic effects. When we combine our CNN with the power spectrum, the baryonic effects degrade the constraint in $\Omega_\mathrm{m}-\sigma_8$ space by a factor of 2.4, compared to the much worse degradation by a factor of 4.7 or 3.7 from either method alone.