The Local Bubble: a magnetic veil to our Galaxy

TL;DR

This paper models the magnetic field structure of the Local Bubble using Planck dust polarization data, revealing a highly deformed local magnetic field with different orientations towards the Galactic poles.

Contribution

It introduces an analytical model of the Local Bubble's magnetic shell and fits it to observational data, providing a new framework for 3D magnetic field modeling in the local interstellar medium.

Findings

Magnetic field is highly deformed around the Local Bubble.

Significant directional differences in magnetic field towards north and south Galactic poles.

Provides a methodological framework for 3D magnetic field modeling.

Abstract

The magnetic field in the local interstellar medium does not follow the large-scale Galactic magnetic field. The local magnetic field has probably been distorted by the Local Bubble, a cavity of hot ionized gas extending all around the Sun and surrounded by a shell of cold neutral gas and dust. However, so far no conclusive association between the local magnetic field and the Local Bubble has been established. Here we develop an analytical model for the magnetic field in the shell of the Local Bubble, which we represent as an inclined spheroid, off-centred from the Sun. We fit the model to Planck dust polarized emission observations within 30 deg of the Galactic poles. We find a solution that is consistent with a highly deformed magnetic field, with significantly different directions towards the north and south Galactic poles. This work sets a methodological framework for modelling the three-dimensional (3D) structure of the magnetic field in the local interstellar medium, which is a most awaited input for large-scale Galactic magnetic field models.