Synthetic Observations of Magnetic Fields in Protostellar Cores

TL;DR

This study uses 3D magnetohydrodynamic simulations to analyze magnetic field and outflow alignments in protostellar cores, producing synthetic dust polarization observations that match real data and reveal how magnetic field strength influences alignment and polarization.

Contribution

It introduces a method to compare simulated magnetic field and outflow orientations with observations using synthetic polarization maps, highlighting the impact of magnetic field strength on alignment.

Findings

Less magnetized cores show random alignment consistent with observations.

Fractional polarization increases when magnetic fields are in the plane of the sky.

Outflow directions change significantly over early protostellar evolution.

Abstract

The role of magnetic fields in the early stages of star formation is not well constrained. In order to discriminate between different star formation models, we analyze 3D magnetohydrodynamic simulations of low-mass cores and explore the correlation between magnetic field orientation and outflow orientation over time. We produce synthetic observations of dust polarization at resolutions comparable to millimeter-wave dust polarization maps observed by CARMA and compare these with 2D visualizations of projected magnetic field and column density. Cumulative distribution functions of the projected angle between the magnetic field and outflow show different degrees of alignment in simulations with differing mass-to-flux ratios. The distribution function for the less magnetized core agrees with observations finding random alignment between outflow and field orientations, while the more magnetized core exhibits stronger alignment. We find that fractional polarization increases when the system is viewed such that the magnetic field is close to the plane of the sky, and the values of fractional polarization are consistent with observational measurements. The simulation outflow, which reflects the underlying angular momentum of the accreted gas, changes direction significantly over the first $\sim0.1$ Myr of evolution. This movement could lead to the observed random alignment between outflows and the magnetic fields in protostellar cores.