Abstract/Details

Turbulence in the interstellar medium


1999 1999

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Abstract (summary)

The multivariate technique of principal component analysis (PCA) is a powerful statistical tool with which to describe spectral line imaging observations of the molecular interstellar medium. In particular, as formulated by Heyer & Schloerb (1997), PCA can retrieve statistical information about the velocity fields within the interstellar gas. However, the nature of the transformation of the intrinsic velocity field onto an observable velocity axis is extremely complex if the velocity field is macroturbulent. In this work, PCA is used to show that interstellar velocity fields are characterized by stochastic fluctuations on all measurable scales (i.e., are macroturbulent) and to obtain a quantitative measure of the turbulent velocity dispersion as a function of scale. To relate the measurable statistical information to intrinsic velocity field statistics, an ensemble of artificial density and velocity fields are translated onto the observational domain, utilizing non-LTE radiative transfer calculations. The intrinsic statistical properties of these fields are well-defined and accurately known, which allows the retrieved information to be calibrated to the intrinsic information. Additional results dealing with the instrumental noise and telescope beam-smearing effects on the PCA method are derived and demonstrated. An application of the reformulated method is carried out on an ensemble of outer Galaxy molecular spectral line imaging observations to obtain the first calibrated measurements of interstellar cloud velocity fields.

Indexing (details)


Subject
Astronomy;
Astrophysics
Classification
0606: Astronomy
0606: Astrophysics
Identifier / keyword
Pure sciences, Interstellar, Principle component analysis, Spectral line imaging, Turbulence, Velocity
Title
Turbulence in the interstellar medium
Author
Brunt, Christopher Michael
Number of pages
142
Publication year
1999
Degree date
1999
School code
0118
Source
DAI-B 60/05, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780599328723, 059932872X
Advisor
Heyer, Mark H.
University/institution
University of Massachusetts Amherst
University location
United States -- Massachusetts
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
9932298
ProQuest document ID
304529913
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/304529913
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