# Detection of Polarized Infrared Emission by Polycyclic Aromatic Hydrocarbons in the MWC 1080 Nebula

## TL;DR

This paper reports the first definitive detection of polarized PAH emission at 11.3 μm in the MWC 1080 nebula, revealing unexpectedly high polarization levels that challenge existing models of PAH alignment.

## Contribution

It provides the first confirmed measurement of polarized PAH emission in an astrophysical environment, highlighting the need to reconsider PAH alignment mechanisms.

## Key findings

- Detected 1.9% polarization at 11.3 μm in MWC 1080 nebula
- Challenges current models of PAH alignment with magnetic fields
- Suggests resonance paramagnetic relaxation as a possible alignment process

## Abstract

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in astrophysical environments, as revealed by their pronounced emission features at 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 $\mu$m commonly ascribed to the C--H and C--C vibrational modes. Although these features have long been predicted to be polarized, previous searches for PAH polarization led to null or, at best, tentative detections. Here we report the definite detection of polarized PAH emission at 11.3 $\mu$m in the nebula associated with the Herbig Be star MWC 1080. We measure a polarization degree of 1.9$\pm$0.2\%, which is unexpectedly high compared to models. This poses a challenge in the current understanding of the alignment of PAHs, which is required to polarize the PAH emission but thought to be substantially suppressed. PAH alignment with a magnetic field via a resonance paramagnetic relaxation process may account for such a high level of polarization.