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Turbulent Mixing in Wind-Blown HII Regions

Published online by Cambridge University Press:  12 April 2016

D. Breitschwerdt  and
F.D. Kahn
D. Breitschwerdt
Affiliation:
Max-Planck-Institut für Kemphysik, D-6900 Heidelberg, Postfach 10 39 80, FRG
F.D. Kahn
Affiliation:
Department of Astronomy, The University, Manchester MIS 9PL, England

Abstract

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Turbulent mixing between an ionization bounded HII region and a hot shocked stellar wind (HSSW), which keeps it under pressure, is examined. Recently we have shown that acoustic disturbances can grow there to finite amplitude in a time scale which is comparable to the sound crossing time in the HII layer. The resulting turbulence will then stretch fluid elements and the frozen-in magnetic field. A condition under which turbulence can decay down to the viscous scale, where mixing is very efficient, is derived. For a uniform and plane parallel magnetic field Bo and a constant density ρo of the ambient medium, we find that efficient mixing takes place near the polar regions. Subsequently the rate of mass addition to the hot bubble is calculated and it is shown that catastrophic cooling is likely to occur. In the case of NGC 6334(A) it seems that this has just happened and we predict an upper limit for Bo of 4 x 10-5 gauss there. This model may also explain the existence of highly ionized species (e.g. OVI), soft X-rays and high velocity flows of the order of 100 km/s.

Type
I. Molecular Clouds, Star Formation And HII Regions
Information
International Astronomical Union Colloquium , Volume 120: Structure and Dynamics of the Interstellar Medium , 1989 , pp. 117 - 121
Copyright
Copyright © Springer-Verlag 1989

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