# Dust polarization modeling at large-scale over the Northern Galactic cap using EBHIS and Planck data

## TL;DR

This paper develops a detailed dust polarization model using Planck and HI survey data to improve the separation of Galactic dust emission from the CMB B-mode polarization signal, aiding future cosmological measurements.

## Contribution

It introduces a seven-parameter dust model that accurately reproduces observed dust polarization statistics over the northern Galactic cap.

## Key findings

- Model reproduces observed polarization statistics
- Uses HI data as a proxy for dust intensity
- Assists in separating Galactic dust from CMB signals

## Abstract

The primary source of systematic uncertainty in the quest for the B-mode polarization of the Cosmic Microwave Background (CMB) introduced by primordial gravitational waves is polarized thermal emission from Galactic dust. Therefore, accurate characterization and separation of the polarized thermal dust emission is an essential step in distinguishing such a faint CMB B-mode signal. We provide a modelling framework to simulate polarized thermal dust emission based on the model described in Ghosh et al. (2017), making use of both the Planck dust and Effelsberg-Bonn HI surveys over the northern Galactic cap. Our seven-parameter dust model, incorporating both HI gas in three different column density templates as a proxy for spatially variable dust intensity and a phenomenological model of Galactic magnetic field, is able to reproduce both 1- and 2-point statistics of the observed dust polarization maps seen by Planck at 353 GHz over a selected low-column density region in the northern Galactic cap. This work has important applications in assessing the accuracy of component separation methods and in quantifying the confidence level of separating polarized Galactic emission and the CMB B-mode signal, as is needed for ongoing and future CMB missions.