Statistics of Galactic Synchrotron and Dust Foregrounds: Spectra, PDFs and Higher-Order Moments

TL;DR

This paper analyzes the statistical properties of Galactic synchrotron and dust emissions, linking turbulence models to observed spectra and polarization, and proposing models that explain the angular spectra in different Galactic regions.

Contribution

It provides a comprehensive statistical analysis connecting Galactic turbulence models with observed synchrotron and dust polarization spectra, including new model calculations for angular spectra.

Findings

MHD turbulence explains high-latitude synchrotron emission.

Extended halo or two-component models fit observed spectra.

Predicted dust polarization spectrum follows a specific power law.

Abstract

We present statistical analysis of diffuse Galactic synchrotron emission and polarized thermal emission from dust. Both Galactic synchrotron emission and polarized thermal emission from dust reflect statistics of magnetic field fluctuations and, therefore, Galactic turbulence. We mainly focus on the relation between observed angular spectra and underlying turbulence statistics. Our major findings are as follows. First, we find that magnetohydrodynamic (MHD) turbulence in the Galaxy can indeed explain diffuse synchrotron emission from high galactic latitude. Our model calculation suggests that either a one-component extended halo model or a two-component model, an extended halo component (scale height > 1kpc) plus a local component, can explain the observed angular spectrum of the synchrotron emission. However, discrete sources seem to dominate the spectrum for regions near the Galactic plane. Second, we study how star-light polarization is related with polarized emission from thermal dust. We also discuss the expected angular spectrum of polarized emission from thermal dust. Our model calculations suggest that C_l\propto l^{-11/3} for l > 1000 and a shallower spectrum for l < 1000.