# Modeling the magnetized Local Bubble from dust data

**Authors:** V. Pelgrims, K. Ferrière, F. Boulanger, R. Lallement, L. Montier  
**arXiv:** [1911.09691](https://arxiv.org/abs/1911.09691)  
**Date:** 2019-11-21  
**Summary page:** https://www.summarizepaper.com/en/paper/1911.09691v2/

## Key points

- The Local Bubble (LB) is a cavity of hot plasma created by supernova explosions and surrounded by a shell of cold, dusty gas in which the Sun is embedded.
- Understanding the local distortion of the Galactic magnetic field associated with the LB is crucial for modeling interstellar polarization data at high Galactic latitudes.
- Authors present a new approach to modeling the local structure of the Galactic magnetic field on the LB scale using three-dimensional (3D) maps of the local interstellar medium (ISM).
- The authors extracted the geometry of the LB shell's inner surface from 3D dust extinction maps of the local ISM and expanded it in spherical harmonics up to a variable maximum multipole degree to control complexity for modeled surfaces.
- An analytical model for ordered magnetic fields in shells was applied to these modeled surfaces successfully fitted to Planck 353 GHz dust polarized emission maps over Galactic polar caps.
- For each polar cap, direction of mean magnetic field derived from dust polarization was found consistent with Faraday spectra of nearby diffuse synchrotron emission.
- This work presents a new methodology useful for modeling different components of local ISM and dust polarized emission - long-awaited input for studies on polarized foregrounds for cosmic microwave background research.
- The findings provide critical insights into understanding how magnetic fields are distributed within our galaxy's Local Bubble region and will help improve models used in future research on interstellar polarization data at high Galactic latitudes.

## Summary

The Local Bubble (LB) is a cavity of hot plasma created by supernova explosions and surrounded by a shell of cold, dusty gas in which the Sun is embedded. Understanding the local distortion of the Galactic magnetic field associated with the LB is crucial for modeling interstellar polarization data at high Galactic latitudes. In this paper, authors V. Pelgrims, K. Ferrière, F. Boulanger, R. Lallement, and L. Montier present a new approach to modeling the local structure of the Galactic magnetic field on the LB scale using three-dimensional (3D) maps of the local interstellar medium (ISM). The authors extracted the geometry of the LB shell's inner surface from 3D dust extinction maps of the local ISM and expanded it in spherical harmonics up to a variable maximum multipole degree to control complexity for modeled surfaces. Next, an analytical model for ordered magnetic fields in shells was applied to these modeled surfaces successfully fitted to Planck 353 GHz dust polarized emission maps over Galactic polar caps. For each polar cap, direction of mean magnetic field derived from dust polarization (with prior that field points toward longitude $90^\circ \pm 90^\circ$) was found consistent with Faraday spectra of nearby diffuse synchrotron emission. This work presents a new methodology useful for modeling different components of local ISM and dust polarized emission - long-awaited input for studies on polarized foregrounds for cosmic microwave background research. The findings provide critical insights into understanding how magnetic fields are distributed within our galaxy's Local Bubble region and will help improve models used in future research on interstellar polarization data at high Galactic latitudes.