Journal ArticleDOI
Self-similar collapse of isothermal spheres and star formation.
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In this paper, the problem of the gravitational collapse of isothermal spheres by applying the similarity method to the gas-dynamic flow is considered, and two types of similarity solutions are obtained: one is the prototype for starting states which correspond to unstable hydrostatic equilibrium; the other, for states where the mass of the cloud slightly exceeds the maximum limit allowable for hydrostatic equilibria.Abstract:
We consider the problem of the gravitational collapse of isothermal spheres by applying the similarity method to the gas-dynamic flow. We argue that a previous solution obtained by Larson and Penston to describe the stages prior to core formation is physically artificial; however, we find that the flow following core formation does exhibit self-similar properties.The latter similarity solution shows that the inflow in the dense central regions proceeds virtually at free-fall before the material is arrested by a strong radiating shock upon impact with the surface of the core. Two types of similarity solutions are obtained: one is the prototype for starting states which correspond to unstable hydrostatic equilibrium; the other, for states where the mass of the cloud slightly exceeds the maximum limit allowable for hydrostatic equilibrium. In both cases, an r/sup -2/ law holds for the density distribution in the static or nearly static outer envelope, and an r/sup -3///sup 2/ law holds for the freely falling inner envelope. Rapid infall is initiated at the head of the expansion wave associated with the dropping of the central regions from beneath the envelope. A numerical example is presented which is shown to be in good agreement with the envelopemore » dynamics obtained in previous studies of star formation using hydrodynamic codes.« lessread more
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Warm cores around regions of low-mass star formation
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LIME - a flexible, non-LTE line excitation and radiation transfer method for millimeter and far-infrared wavelengths
TL;DR: In this paper, the authors present a new code for solving the molecular and atomic excitation and radiation transfer problem in a molecular gas and predicting emergent spectra. This code works in arbitrary three dimensional geometry using unstructured Delaunay latices for the transport of photons.
Journal ArticleDOI
HCN in Bok Globules: A Good Tracer of Collapsing Cores
TL;DR: In this paper, a survey of dense cores in a sample of 24 star-forming and quiescent Bok globules was conducted, where HCN emission was detected toward 11 of 13 globules containing embedded point sources, with no detection among 11 starless globules.
Journal ArticleDOI
Orbital and Mass Ratio Evolution of Protobinaries Driven by Magnetic Braking
Bo Zhao,Zhi-Yun Li +1 more
TL;DR: In this paper, the authors demonstrate numerically, using the ENZO-MHD code, that a magnetic field of the observed strength can drastically change two of the basic quantities of a binary system: the orbital separation and mass ratio of the two components.
Journal ArticleDOI
The Formation Conditions of the Wide Binary Class 0 Protostars within BHR 71
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