Magnetic Field Structure in Spheroidal Star-Forming Clouds

TL;DR

This paper presents a magnetic field model for star-forming clouds of various shapes, aiding in testing flux freezing and estimating magnetic field strength through polarization pattern analysis.

Contribution

The study introduces a scalable analytic model for magnetic field structures in spheroidal star-forming clouds, including predictions of polarization patterns and field strengths.

Findings

Model estimates local magnetic field strength and direction.

Polarization angle predictions agree within 1-10 degrees with simulations.

Provides analytic expressions for matching observed polarization patterns.

Abstract

A model of magnetic field structure is presented to help test the prevalence of flux freezing in star-forming clouds of various shapes, orientations, and degrees of central concentration, and to estimate their magnetic field strength. The model is based on weak-field flux freezing in centrally condensed Plummer spheres and spheroids of oblate and prolate shape. For a spheroid of given density contrast, aspect ratio, and inclination, the model estimates the local field strength and direction, and the global field pattern of hourglass shape. Comparisons with a polarization simulation indicate typical angle agreement within 1 - 10 degrees. Scalable analytic expressions are given to match observed polarization patterns, and to provide inputs to radiative transfer codes for more accurate predictions. The model may apply to polarization observations of dense cores, elongated filamentary clouds, and magnetized circumstellar disks.