Synthetic Polarization Maps of an Outflow Zone from Magnetohydrodynamic Simulations

TL;DR

This study uses magnetohydrodynamic simulations and radiative transfer modeling to produce synthetic polarization maps, which are compared with observations of star-forming regions to understand magnetic field structures in outflow zones.

Contribution

It presents the first detailed synthetic polarization maps of protostellar outflow zones from resistive nonideal MHD simulations, aiding interpretation of observational polarization data.

Findings

Synthetic polarization maps agree with observations when the magnetic axis is tilted at 15°.

Comparison helps resolve the ambiguity of polarization orientation relative to magnetic fields.

Results support the toroidal magnetic field structure in outflow regions.

Abstract

The canonical theory of star formation in a magnetized environment predicts the formation of hourglass-shaped magnetic fields during the prestellar collapse phase. In protostellar cores, recent observations reveal complex and strongly distorted magnetic fields in the inner regions that are sculpted by rotation and outflows. We conduct resistive, nonideal magnetohydrodynamic (MHD) simulations of a protostellar core and employ the radiative transfer code POLARIS to produce synthetic polarization segment maps. Comparison of our mock-polarization maps based on the toroidal-dominated magnetic field in the outflow zone with the observed polarization vectors of SiO lines in Orion Source I shows a reasonable agreement when the magnetic axis is tilted at an angle $\theta = 15^{\circ}$ with respect to the plane-of-sky and if the SiO lines have a net polarization parallel to the local magnetic field. Although the observed polarization is from SiO lines and our synthetic maps are due to polarized dust emission, a comparison is useful and allows us to resolve the ambiguity of whether the line polarization is parallel or perpendicular to the local magnetic field direction.