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Grain Sedimentation and the Old Open Clusters NGC2420 and NGC2506

Published online by Cambridge University Press:  25 April 2016

J. Lattanzio
J. Lattanzio*
Affiliation:
Department of Mathematics, Monash University
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Extract

Star formation is believed to occur in interstellar clouds consisting of both gas and grains. Under the gravitational influence of such a cloud the constituent dust grains sediment toward the centre, and both calculations and implications of this sedimentation have been published by many authors (McCrea and Williams 1965; Horedt 1973, 1976; Prentice 1976; Krautschneider 1977; Flannery and Krook 1978; and others). Two main results from these calculations warrant our attention. Firstly, the timescale for appreciable sedimentation Ts ≃ 107 -108 years, which is consistent with age estimates of many clouds (Harrison 1978, Blitz and Shu 1980). Secondly, the sedimentation proceeds more rapidly for larger grains. This leads to an increase of mean grain size toward the centre of the cloud.

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Contributions
Information
Publications of the Astronomical Society of Australia , Volume 5 , Issue 2 , 1983 , pp. 232 - 235
Copyright
Copyright © Astronomical Society of Australia 1983

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