Magnetic Fields and the Triaxiality of Molecular Cloud Cores

Abstract

We make the hypothesis that molecular cloud fragments are triaxial bodies with a large scale magnetic field oriented along the short axis. While consistent with theoretical expectations, this idea is supported by magnetic field strength data, which show strong evidence for flattening along the direction of the mean magnetic field. It is also consistent with early submillimeter polarization data, which show that the projected direction of the magnetic field is often slightly misaligned with the projected minor axis of a molecular cloud core, i.e., the offset angle $Ψ$ is nonzero. We calculate distributions of $Ψ$ for various triaxial bodies, when viewed from a random set of viewing angles. The highest viewing probability always corresponds to $Ψ=0^{\circ}$, but there is a finite probability of viewing all nonzero $Ψ$, including even $Ψ=90^{\circ}$; the average offset typically falls in the range $10^{\circ}-30^{\circ}$ for triaxial bodies most likely to satisfy observational and theoretical constraints.