Simulating and Characterizing Non-Gaussian Small-Scale Polarized Emission

Abstract

Galactic foregrounds present a major challenge for cosmic microwave background (CMB) cosmology as their amplitudes exceed the target primordial $B$-mode signal. While small-scale interstellar medium (ISM) emission is expected to be highly complex, current foreground simulations cannot reproduce the filamentary, non-Gaussian features of ISM structure in a stochastic way. To address this gap, we introduce a framework for generating stochastic small-scale foreground emission, using polarized synchrotron observations as an example use case. This method is capable of producing many independent realizations that additionally inherit morphological information from large angular scales. The underlying structural complexity incorporates anisotropic, multifractal, and advected non-Gaussian features that are tunable with a small number of parameters that carry physical interpretations. Because standard power spectra do not describe the complex phase coherence required for the structural complexity, we evaluate the synthetic fields using higher-order statistics, demonstrating that the Minkowski functionals and structure functions partially capture varying degrees of non-Gaussianity. This work lays the necessary foundation for new foreground simulation suites with stochastic realizations of possible non-Gaussian structure.

arXiv comment25 pages, 19 figures, submitted to APJ