Modelling and simulation of large-scale polarized dust emission over the southern Galactic cap using the GASS HI data

TL;DR

This paper develops a dust emission model based on HI data and magnetic field phenomenology to replicate Planck observations of polarized dust over the southern Galactic cap, aiding CMB foreground analysis.

Contribution

It introduces a novel dust modeling approach that combines HI maps and magnetic field descriptions to accurately simulate polarized dust emission at high Galactic latitudes.

Findings

Successfully reproduces Planck 353 GHz dust polarization data

Demonstrates the model's utility for testing component separation methods

Provides a tool for studying dust decorrelation with frequency

Abstract

The Planck survey has quantified polarized Galactic foregrounds and established that they are a main limiting factor in the quest for the cosmic microwave background (CMB) B-mode signal induced by primordial gravitational waves during cosmic inflation. Accurate separation of the Galactic foregrounds therefore binds this quest to our understanding of the magnetized interstellar medium (ISM). The two most relevant empirical results from analysis of Planck data are line of sight depolarization arising from fluctuations of the Galactic magnetic field orientation and alignment of filamentary dust structures with the magnetic field at high Galactic latitude. Furthermore, Planck and HI emission data in combination indicate that most of the filamentary dust structures are in the cold neutral medium. The goal of this paper is to test whether these salient observational results, taken together, can account fully for the statistical properties of the dust polarization over a selected low column density region comprising 34 % of the southern Galactic cap ($b \le -30\deg$). To do this, we construct a dust model that incorporates HI column density maps as tracers of the dust intensity structures and a phenomenological description of the Galactic magnetic field. By adjusting the parameters of the dust model, we were able to reproduce the Planck dust observations at 353 GHz in the selected region. Realistic simulations of the polarized dust emission enabled by such a dust model are useful for testing the accuracy of component separation methods, studying non-Gaussianity, and constraining the amount of decorrelation with frequency.