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A dynamical model for the dusty ring in the Coalsack

Hennebelle, P., Whitworth, Anthony Peter and Goodwin, S. P. 2006. A dynamical model for the dusty ring in the Coalsack. Astronomy and Astrophysics 451 (1) , pp. 141-146. 10.1051/0004-6361:20054634

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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 $0.4\,{\rm km}\,{\rm s}^{-1}$. 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, $E_{{\rm TURB}}/\vert E_{{\rm GRAV}}\vert \leq 2\%$. Protostar formation should occur in about 40 000 years.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: ISM: clouds; stars: formation; hydrodynamics; instabilities; shock waves
Additional Information: Pdf uploaded in accordance with publisher's policy at (accessed 17/04/2014)
Publisher: EDP Sciences
ISSN: 0004-6361
Date of First Compliant Deposit: 30 March 2016
Last Modified: 04 Jun 2017 04:55

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