Dispersion of Observed Position Angles of Submillimeter Polarization in Molecular Clouds

TL;DR

This paper reassesses magnetic field strengths in molecular clouds by comparing submillimeter polarization data with simulations, emphasizing higher resolution observations and concluding that magnetic energy is comparable to turbulent kinetic energy.

Contribution

It introduces an improved analysis approach incorporating higher resolution data to better estimate magnetic energy in molecular clouds.

Findings

Magnetic energy in GMCs is at least as large as turbulent kinetic energy.

Higher resolution observations refine magnetic field estimates.

Comparison with simulations supports a dominant magnetic energy presence.

Abstract

One can estimate the characteristic magnetic field strength in GMCs by comparing submillimeter polarimetric observations of these sources with simulated polarization maps developed using a range of different values for the assumed field strength. The point of comparison is the degree of order in the distribution of polarization position angles. In a recent paper by H. Li and collaborators, such a comparison was carried out using SPARO observations of two GMCs, and employing simulations by E. Ostriker and collaborators. Here we reexamine this same question, using the same data set and the same simulations, but using an approach that differs in several respects. The most important difference is that we incorporate new, higher angular resolution observations for one of the clouds, obtained using the Hertz polarimeter. We conclude that the agreement between observations and simulations is best when the total magnetic energy (including both uniform and fluctuating field components) is at least as large as the turbulent kinetic energy.