On Far-Infrared and Submm Circular Polarization

TL;DR

This paper discusses how variations in dust grain alignment in space can produce circular polarization in infrared and submillimeter wavelengths, which could reveal magnetic field structures and grain alignment mechanisms.

Contribution

It provides theoretical predictions of circular polarization levels in different interstellar environments, highlighting potential observability and scientific implications.

Findings

Circular polarization is negligible in diffuse interstellar medium.

Detectable levels of circular polarization may occur in infrared dark clouds.

Measurement of circular polarization can inform magnetic field and grain alignment studies.

Abstract

Interstellar dust grains are often aligned. If the grain alignment direction varies along the line of sight, the thermal emission becomes circularly-polarized. In the diffuse interstellar medium, the circular polarization at far-infrared and submm wavelengths is predicted to be very small, and probably unmeasurable. However, circular polarization may reach detectable levels in infrared dark clouds and protoplanetary disks. Measurement of circular polarization could help constrain the structure of the magnetic field in infrared dark clouds, and may shed light on the mechanisms responsible for grain alignment in protoplanetary disks.