Ascertaining the role of magnetic fields in star formation through synthetic polarization observations

Magnetic fields are important in star formation, but cannot be measured directly. Instead, since many asymmetrical dust grains are aligned with the local magnetic field, magnetic field structures can be estimated from linear polarization observations of dust emission. Using POLARIS, a radiative transfer code, we post-processed a magnetohydrodynamic (MHD) simulation snapshot that includes 289 stars of various masses and luminosities in a cubical box with side lengths of 4 pc. We compared polarization in the cases of perfect alignment and radiative alignment torques, as well as at different wavelengths observable with SOFIA (starting at 53 μm) and ALMA (ending at 1.3 mm). We also looked at distance scales ranging from about 10,000 AU to 100,000 AU. Generally over all the wavelengths and distances studied, linear polarization was a good indicator of magnetic field lines. However, we found that in some dense, high optical depth areas of the star-forming region, the polarization patterns change with wavelength. This change is attributed to the difference between absorption and emission of light by the dust.