Journal Article

Self-consistent analysis of OH Zeeman observations

Richard M. Crutcher, Nicholas Hakobian and Thomas H. Troland

in Monthly Notices of the Royal Astronomical Society: Letters

Published on behalf of The Royal Astronomical Society

Volume 402, issue 1, pages L64-L66
Published in print February 2010 |
Published online February 2010 | e-ISSN: 1745-3933 | DOI: http://dx.doi.org/10.1111/j.1745-3933.2009.00802.x

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Abstract

Crutcher et al. used OH Zeeman observations of four nearby molecular dark clouds to show that the ratio of mass to magnetic flux was smaller in the ∼0.1 pc cores than in the ∼1 pc envelopes, in contradiction to the prediction of ambipolar diffusion driven core formation. A crucial assumption was that the magnetic field direction is nearly the same in the envelope and core regions of each cloud. Mouschovias & Tassis have argued that the data are not consistent with this assumption, and presented a new analysis that changes the conclusions of the study. Here, we show that the data are in fact consistent with the nearly uniform field direction assumption; hence, the original study is internally self-consistent and the conclusions are valid under the assumptions that were made. We also show that the Mouschovias & Tassis model of magnetic fields in cloud envelopes is inconsistent with their own analysis of the data. However, the data do not rule out a more complex field configuration that future observations may discern.

Keywords: stars: formation; ISM: clouds; ISM: evolution; ISM: magnetic fields

Journal Article.  1915 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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