Synthetic dust polarization emission maps at 353 GHz for an observer placed inside a Local Bubble-like cavity

TL;DR

This study uses magnetohydrodynamic simulations to generate synthetic polarized dust emission maps at 353 GHz, revealing the influence of the Local Bubble on observed polarization patterns and comparing them with Planck satellite data.

Contribution

It introduces a novel simulation-based approach to model dust polarization within a Local Bubble-like cavity, enhancing understanding of local ISM magnetic field structures.

Findings

The local cavity acts as a polarization filter affecting emission from beyond.

Synthetic magnetic field patterns qualitatively match Planck observations at high latitudes.

Distinguishing Galactic cap topology from polarization data alone is challenging.

Abstract

We present a study of synthetic observations of polarized dust emission at 353 GHz as seen by an observer within a cavity in the interstellar medium (ISM). The cavity is selected from a magnetohydrodynamic simulation of the local ISM with time-dependent chemistry, star formation, and stellar feedback in form of supernova explosions with physical properties comparable to the Local Bubble ones. We find that the local density enhancement together with the coherent magnetic field in the cavity walls makes the selected candidate a translucent polarization filter to the emission coming from beyond its domains. This underlines the importance of studying the Local Bubble in further detail. The magnetic field lines inferred from synthetic dust polarization data are qualitatively in agreement with the all-sky maps of polarized emission at 353 GHz from the Planck satellite in the latitudes interval 15deg <= |b| <= 65deg. As our numerical simulation allows us to track the Galactic midplane only out to distances of 250 pc, we exclude the region |b|<15deg from our analysis. At large Galactic latitudes, our model exhibits a high degree of small-scale structures. On the contrary, the observed polarization pattern around the Galactic poles is relatively coherent and regular, and we argue that the global toroidal magnetic field of the Milky Way is important for explaining the data at |b| > 65deg. We show that from our synthetic polarization maps, it is difficult to distinguish between an open and a closed Galactic cap using the inferred magnetic field morphology alone.