Issue |
A&A
Volume 451, Number 1, May III 2006
|
|
---|---|---|
Page(s) | 141 - 146 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20054634 | |
Published online | 25 April 2006 |
A dynamical model for the dusty ring in the Coalsack
1
École Normale Supérieure, Laboratoire de Radioastronomie Millimétrique, 24 rue Lhomond, 75231 Paris Cedex 05, France e-mail: Patrick.Hennebelle@ens.fr
2
School of Physics & Astronomy, Cardiff University, 5 The Parade, Cardiff CF24 3YB, Wales, UK e-mail: Anthony.Whitworth@astro.cf.ac.uk
3
Department of Physics & Astronomy, University of Sheffield, Hicks Building, Housfield Road, Sheffield S3 7RH, UK e-mail: S.Goodwin@sheffield.ac.uk
Received:
18
July
2005
Accepted:
2
February
2006
Lada et al. recently presented a detailed near-infrared extinction map
of Globule G2 in the Coalsack molecular cloud complex, showing that this starless core has a
well-defined central extinction minimum. We propose a model for G2 in which a rapid increase
in external pressure is driving an approximately symmetric compression wave into the core.
The rapid increase in external pressure could arise because the core has recently been
assimilated by the Coalsack cloud complex, or because the Coalsack has recently been created by
two large-scale converging flows. The resulting compression wave has not yet converged on the centre
of the core, so there is a central rarefaction. The compression wave has increased the density
in the swept-up gas by about a factor of ten, and accelerated it inwards to speeds of order
.
It is shown that even a low initial level of turbulence completely
destroys the coherence of the ring, as seen in projection. In the
scenario of strong external compression that we are proposing this
implies that the initial turbulent energy in the globule was low,
. Protostar formation
should occur in about 40 000 years.
Key words: ISM: clouds / stars: formation / hydrodynamics / instabilities / shock waves
© ESO, 2006
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