Journal Article

Evidence for dynamically important magnetic fields in molecular clouds

Hua-bai Li, Raymond Blundell, Abigail Hedden, Jonathan Kawamura, Scott Paine and Edward Tong

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 411, issue 3, pages 2067-2075
Published in print March 2011 | ISSN: 0035-8711
Published online February 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.17839.x
Evidence for dynamically important magnetic fields in molecular clouds

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Recent observational evidence that magnetic fields are dynamically important in molecular clouds, compared to self-gravity and turbulence, is reviewed and illustrated with data from the NGC 2024 region. One piece of evidence, turbulence anisotropy, was found in the diffuse envelope of a cloud (Av≈ 1; Heyer et al. 2008); our data further suggest turbulence anisotropy in the cloud (Av > 7) and even near the cloud core (Av∼ 100). The data also show that magnetic fields can channel gravitational contraction even for a region with supercritical N(H2)/2Blos ratio (the ratio between the observed column density and two times the line-of-sight observed field strength), a parameter which has been widely used by observers to estimate core mass-to-flux ratios. Although the mass-to-flux ratio is constant under the flux-freezing condition, we show that N(H2)/2Blos grows with time if gravitational contraction is anisotropic due to magnetic fields.

Keywords: MHD; turbulence; stars: formation; ISM: clouds; ISM: kinematics and dynamics; ISM: magnetic fields

Journal Article.  5291 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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