Wavelet Flow For Extragalactic Foreground Simulations

TL;DR

This paper introduces Wavelet Flow models to accurately simulate correlated extragalactic foregrounds in CMB observations, capturing their complex non-Gaussian statistics for improved cosmological data analysis.

Contribution

The study demonstrates that Wavelet Flow models can effectively generate high-fidelity, correlated CMB secondary fields, advancing field-level modeling of non-Gaussian foregrounds.

Findings

Power spectra within a few percent of inputs across scales

Accurate Minkowski functional reproduction

Effective multiscale fine-tuning of model parameters

Abstract

Extragalactic foregrounds in cosmic microwave background (CMB) observations are both a source of cosmological and astrophysical information and a nuisance to the CMB. Effective field-level modeling that captures their non-Gaussian statistical distributions is increasingly important for optimal information extraction, particularly given the precise and low-noise observations from current and upcoming experiments. We explore the use of Wavelet Flow (WF) models to tackle the novel task of modeling the field-level probability distributions of multi-component CMB secondaries and foreground. Specifically, we jointly train correlated CMB lensing convergence ($\kappa$) and cosmic infrared background (CIB) maps with a WF model and obtain a network that statistically recovers the input to high accuracy -- the trained network generates samples of $\kappa$ and CIB fields whose average power spectra are within a few percent of the inputs across all scales, and whose Minkowski functionals are similarly accurate compared to the inputs. Leveraging the multiscale architecture of these models, we fine-tune both the model parameters and the priors at each scale independently, optimizing performance across different resolutions. These results demonstrate that WF models can accurately simulate correlated components of CMB secondaries, supporting improved analysis of cosmological data. Our code and trained models can be found here (https://github.com/matiwosm/HybridPriorWavletFlow.git).