Molecular Clouds as Ensembles of Transient Cores

Abstract

We construct models of molecular clouds that are considered as ensembles of transient cores. Each core is assumed to develop in the background gas of the cloud, grow to high density and decay into the background. The chemistry in each core responds to the dynamical state of the gas and to the gas-dust interaction. Ices are deposited on the dust grains in the core's dense phase, and this material is returned to the gas as the core expands to low density. The cores of the ensemble number typically one thousand and are placed randomly in position within the cloud, and are assigned a random evolutionary phase. The models are used to generate molecular line contour maps of a typical dark cloud. These maps are found to represent extremely well the characteristic features of observed maps of the dark cloud L673, which has been observed at both low and high resolutions. The computed maps are found to exhibit the general morphology of the observed maps, and to generate similar sizes of emitting regions, molecular column densities, and the separations between peaks of emissions of various molecular species. The models give insight into the nature of molecular clouds and the dynamical processes occurring within them, and significantly constrain dynamical and chemical processes in the interstellar medium.

29 pages, 8 figures. Accepted for publication in ApJ

References in corpus (6)

• Physical Conditions in Regions of Star Formation
• Systematic Molecular Differentiation in Starless Cores
• Formation and loss of hierarchical structure in two-dimensional MHD simulations of wave-driven turbulence in interstellar clouds
• Rarefaction Shocks, Shock Errors and Low Order of Accuracy in ZEUS
• Evidence for transient clumps and gas chemical evolution in the CS core of L673
• Multitransitional observations of the CS core of L673

Cited by in corpus (9)

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• Simulating the formation of molecular clouds. II. Rapid formation from turbulent initial conditions
• Desorption From Interstellar Ices
• Star formation in Chamaeleon I and III: a molecular line study of the starless core population
• Astrophysics in 2006
• Dense and diffuse gas in dynamically active clouds
• Water Ice Deposition and Growth in Molecular Clouds
• The clumpiness of molecular clouds: HCO+ (3--2) survey near Herbig-Haro objects
• Probing the physical and chemical structure of the CS core in LDN 673. Multitransitional and continuum observations