Far-infrared polarimetry from the Stratospheric Observatory for Infrared Astronomy

TL;DR

This paper explores potential upgrades to the HAWC instrument on SOFIA to enable far-infrared polarimetry, enhancing studies of magnetic fields, dust, and molecular clouds in the interstellar medium.

Contribution

It proposes specific hardware upgrade options for HAWC to incorporate polarimetric capabilities for the first time on SOFIA.

Findings

Evaluation of three upgrade options for polarimetry

Potential to study magnetic fields in various astrophysical environments

Enhanced wavelength-dependent polarization measurements

Abstract

Multi-wavelength imaging polarimetry at far-infrared wavelengths has proven to be an excellent tool for studying the physical properties of dust, molecular clouds, and magnetic fields in the interstellar medium. Although these wavelengths are only observable from airborne or space-based platforms, no first-generation instrument for the Stratospheric Observatory for Infrared Astronomy (SOFIA) is presently designed with polarimetric capabilities. We study several options for upgrading the High-resolution Airborne Wideband Camera (HAWC) to a sensitive FIR polarimeter. HAWC is a 12 x 32 pixel bolometer camera designed to cover the 53 - 215 micron spectral range in 4 colors, all at diffraction-limited resolution (5 - 21 arcsec). Upgrade options include: (1) an external set of optics which modulates the polarization state of the incoming radiation before entering the cryostat window; (2) internal polarizing optics; and (3) a replacement of the current detector array with two state-of-the-art superconducting bolometer arrays, an upgrade of the HAWC camera as well as polarimeter. We discuss a range of science studies which will be possible with these upgrades including magnetic fields in star-forming regions and galaxies and the wavelength-dependence of polarization.