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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Journal ArticleDOI
Formation of the first stars and black holes
TL;DR: In this article, the authors review the current status of knowledge concerning the early phases of star formation during cosmic dawn, including the first generations of stars forming in the lowest mass dark matter halos in which cooling and condensation of gas with primordial composition is possible at very high redshift, and the first generation of massive black holes forming at such early epochs, the so-called black hole seeds.
Journal ArticleDOI
The influence of infall on the properties of protoplanetary discs Statistics of masses, sizes, lifetimes, and fragmentation
O. Schib,O. Schib,C. Mordasini,N. Wenger,G.-D. Marleau,G.-D. Marleau,G.-D. Marleau,Ravit Helled +7 more
TL;DR: In this paper, a population synthesis of protoplanetary discs with a total of 50 000 simulations using a 1D vertically integrated viscous evolution code was performed, and the authors derived the mass, radius, lifetime, and gravitational stability of the disks by studying their evolution from formation to dispersal.
Journal ArticleDOI
The VLA Nascent Disk and Multiplicity Survey of Perseus Protostars (VANDAM). V. 18 Candidate Disks around Class 0 and I Protostars in the Perseus Molecular Cloud
Dominique Segura-Cox,Dominique Segura-Cox,Leslie W. Looney,John J. Tobin,John J. Tobin,Zhi-Yun Li,Robert J. Harris,Robert J. Harris,Sarah Sadavoy,Sarah Sadavoy,Michael M. Dunham,Michael M. Dunham,Claire J. Chandler,Kaitlin M. Kratter,Laura M. Pérez,Carl Melis +15 more
TL;DR: In this article, the authors present the full disk-fit results VANDAM survey of all Class 0 and I protostars in the Perseus molecular cloud, and find statistical evidence that these disks are likely drawn from the same distribution, meaning disk properties may be defined early in the Class 0 phase and do not undergo large changes through the Class I phase.
Journal ArticleDOI
The effect of magnetic fields and ambipolar diffusion on the column density probability distribution function in molecular clouds
TL;DR: In this article, the authors run three-dimensional magnetohydrodynamic simulations including ambipolar diffusion with different initial conditions to see the effect of strong magnetic fields and nonlinear initial velocity perturbations on the evolution of column density PDFs.
Journal ArticleDOI
Dust clearing by radial drift in evolving protoplanetary discs
TL;DR: In this article, the authors used a Monte Carlo method to simulate the evolution of a cluster of protoplanetary discs using a 1D numerical method to viscously evolve each gas disc together with the radial drift of dust particles that have grown to 100 μm in size.
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