Unbound Star-forming Molecular Clouds

Abstract

We explore whether observed molecular clouds could include a substantial population of unbound clouds. Using simulations which include only turbulence and gravity, we are able to match observed relations and naturally reproduce the observed scatter in the cloud size-linewidth coefficient, at fixed surface density. We identify the source of this scatter as a spread in the intrinsic virial parameter. Thus these observational trends do not require that clouds exist in a state of dynamical equilibrium. We demonstrate that cloud virial parameters can be accurately determined observationally with an appropriate size estimator. All our simulated clouds eventually form collapsing cores, regardless of whether the cloud is bound overall. This supports the idea that molecular clouds do not have to be bound to form stars or to have observed properties like those of nearby low-mass clouds.

9 pages, 6 figures, Accepted for publication by MNRAS

References in corpus (6)

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• The relation between gas and dust in the Taurus Molecular Cloud
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• Evolving Molecular Cloud Structure and the Column Density Probability Distribution Function
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• Comparison of Prestellar Core Elongations and Large-Scale Molecular Cloud Structures in the Lupus I Region
• The Properties of Bound and Unbound Molecular Cloud Populations Formed in Galactic Disc Simulations
• Early-stage star forming cloud cores in GLIMPSE Extended Green Objects (EGOs) as traced by organic species