Department

Physics

Document Type

Article

Publication Date

10-2006

Abstract

Aims: We present an analysis of the exceptionally turbulent velocity field in the high Galactic latitude cirrus cloud MBM 3. As in the other translucent clouds in our study (MBM 16 and MBM 40), there is no evidence for internal star formation. However, the large scale velocity variation in this cloud is more pronounced. Methods: We have mapped the cloud in 12CO and 13CO (1-0) at high spatial (0.03 pc) and velocity (0.06 km s-1) resolution. We constructed several velocity probability density functions (PDFs), estimated the turbulent transfer rate, and analyzed the linewidths as a function of the size of randomly chosen regions within the cloud. Results: We find strong shear flows throughout the cloud that can easily power the turbulent motions. The wings of the PDFs are well approximated by a lorentzian distribution. Such distributions, related to Levy processes that are well known to be produced by correlated processes, are an unambiguous diagnostic of the turbulent intermittency. Conclusions: We find that the linewidth-size relation frequently used to indicate the role of turbulence in molecular clouds is not an unambiguous signature of its presence.

Journal

Astronomy and Astrophysics

Journal ISSN

1432-0746

Volume

457

Issue

1

First Page

197

Last Page

206

Digital Object Identifier (DOI)

10.1051/0004-6361:20053962

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