The Link between Magnetic Fields, Filamentary Clouds and Star Formation Efficiency Hua-bai Li MPIA, Heidelberg, Germany
The recent evidence of cloud-anchoring galactic magnetic fields motivates us to study the link between the Galactic fields and the ubiquitous filamentary structures of molecular clouds. The orientation of filamentary molecular clouds in the Gould Belt and their magnetic fields are studied using dust extinction maps and optical stellar polarimetry data. These filaments are a few to tens of parsecs long and many have parallel and/or perpendicular neighbor filaments. This cannot be explained by shocks due to stellar winds or isotropic super-Alfvenic turbulence. More interestingly, we found that the filaments tend to orient either along or perpendicular to the magnetic fields. Most previous studies recognize that strong magnetic fields can guide gravitational contraction and result in filaments perpendicular to the magnetic fields, but few appreciate the fact that fields can also channel sub-Alfvenic turbulence to form filaments aligned with the fields. Dynamically dominant magnetic fields thus can readily explain the two types (parallel and perpendicular) of field-filament configurations we observed. We further analytically show that, assuming virial equilibrium, filaments parallel to fields should have higher star formation efficiency than the other type of filaments Ð a fact which agrees with observations.
Collaborators: Min Fang, PMO, China Thomas Henning, MPIA, Germany Jouni Kainulainen, MPIA, Germany	Key publication