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Recognition and characterization of hierarchical interstellar structure. II - Structure tree statisticsA new method of image analysis is described, in which images partitioned into 'clouds' are represented by simplified skeleton images, called structure trees, that preserve the spatial relations of the component clouds while disregarding information concerning their sizes and shapes. The method can be used to discriminate between images of projected hierarchical (multiply nested) and random three-dimensional simulated collections of clouds constructed on the basis of observed interstellar properties, and even intermediate systems formed by combining random and hierarchical simulations. For a given structure type, the method can distinguish between different subclasses of models with different parameters and reliably estimate their hierarchical parameters: average number of children per parent, scale reduction factor per level of hierarchy, density contrast, and number of resolved levels. An application to a column density image of the Taurus complex constructed from IRAS data is given. Moderately strong evidence for a hierarchical structural component is found, and parameters of the hierarchy, as well as the average volume filling factor and mass efficiency of fragmentation per level of hierarchy, are estimated. The existence of nested structure contradicts models in which large molecular clouds are supposed to fragment, in a single stage, into roughly stellar-mass cores.
Document ID
19920061191
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Houlahan, Padraig
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Scalo, John
(Texas, University Austin, United States)
Date Acquired
August 15, 2013
Publication Date
July 1, 1992
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 393
Issue: 1 Ju
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
92A43815
Funding Number(s)
CONTRACT_GRANT: JPL-958003
CONTRACT_GRANT: NSF AST-86-19738
CONTRACT_GRANT: NAG5-1263
Distribution Limits
Public
Copyright
Other

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