Self‐similar Collapse of Magnetized Molecular Cloud Cores with Ambipolar Diffusion and the “Magnetic Flux Problem” in Star Formation

1998 ◽  
Vol 497 (2) ◽  
pp. 850-858 ◽  
Author(s):  
Zhi‐Yun Li
Keyword(s):  
Star Formation ◽  
Magnetic Flux ◽  
Molecular Cloud ◽  
Ambipolar Diffusion ◽  
Self Similar ◽  
Cloud Cores

scholarly journals Molecules in star formation

1997 ◽  
Vol 178 ◽  
pp. 19-30 ◽  
Author(s):  
F.H. Shu
Keyword(s):  
Star Formation ◽  
Molecular Diagnostics ◽  
Accretion Disks ◽  
Central Star ◽  
Flow Dynamics ◽  
Molecular Outflows ◽  
Self Similar ◽  
Cloud Cores ◽  
Cloud Core ◽  
Review Current

We review current ideas and models in the problem of star formation from molecular cloud cores that are relatively isolated from the influences of other forming stars. We discuss the time scales, flow dynamics, and density and temperature structures applicable to each of the four stages of the entire process: (a) formation of a magnetized cloud core by ambipolar diffusion and evolution to a pivotal state of gravomagneto catastrophe; (b) self-similar collapse of the pivotal configuration and the formation of protostars, disks, and pseudo-disks; (c) onset of a magnetocentrifugally driven, lightly ionized wind from the interaction of an accretion disk and the magnetosphere of the central star, and the driving of bipolar molecular outflows; (d) evolution of pre-main-sequnce stars surrounded by dusty accretion disks. For each of these stages and processes, we consider the characteristics of the molecular diagnostics needed to investigate the crucial aspects of the observational problem.

scholarly journals Star Formation in Molecular Cloud Cores

1987 ◽  
Vol 115 ◽  
pp. 417-434 ◽  
Author(s):  
Frank H. Shu ◽  
Susana Lizano ◽  
Fred C. Adams
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Theoretical Models ◽  
High Mass ◽  
Spectral Energy ◽  
Dark Cloud ◽  
T Tauri ◽  
Analogous Process ◽  
Static Contraction ◽  
Cloud Cores

The problem of gravitational collapse and star formation is entirely different when the ratio of the mass of a molecular cloud Mcl to its magnetic flux Φ is high than when it is low. Magnetically-diluted overall collapse of a large dense core and the formation of an OB association or a bound cluster are the likely outcomes in the former case; quasi-static contraction of many small cores and their ultimate collapse to form a T association, in the latter. In our picture, the birth of a T association in a dark cloud like Taurus proceeds by ambipolar diffusion on a time-scale of ∼ 107 years. As magnetic and turbulent support is gradually lost from a small condensing core, it approaches a state resembling a slowly rotating singular isothermal sphere which, when it passes the brink of instability, collapses from “inside-out,” building up a central protostar and nebular disk. The emergent spectral energy distributions of theoretical models in this stage of protostellar evolution resemble closely those of recently found sources with steep spectra in the infrared. The protostellar phase is ended by the reversal of the infall by an intense stellar wind, whose ultimate source of energy derived from the differential rotation of the star. We argue that the initial breakout is likely to occur along the rotational poles, leading to collimated jets and bipolar outflows. The stellar jet eventually widens to sweep out gas in nearly all 4π steradian, revealing at the center a T Tauri star and a remnant nebular disk. We give rough scaling relations which must apply if an analogous process is to succeed for producing high mass stars.

GRAVITATIONAL COLLAPSE AND FRAGMENTATION OF MOLECULAR CLOUD CORES

2001 ◽  
Vol 10 (02) ◽  
pp. 115-211 ◽  
Author(s):  
LEONARDO DI G. SIGALOTTI ◽  
JAIME KLAPP
Keyword(s):  
Star Formation ◽  
Binary Stars ◽  
Molecular Cloud ◽  
Main Sequence ◽  
Numerical Models ◽  
Present Theory ◽  
Main Sequence Stars ◽  
Consistent Manner ◽  
Cloud Cores ◽  
Observational Knowledge

The detected multiplicity of main-sequence and pre-main-sequence stars along with the emerging evidence for binary and multiple protostars, imply that stars may ultimately form by fragmentation of collapsing molecular cloud cores. These discoveries, coupled with recent observational knowledge of the structure of dense cloud cores and of the properties of young binary stars, provide serious constraints to the theory of star formation. Most theoretical progress in the field of star formation is largely based on numerical calculations of the early collapse and fragmentation of protostellar clouds. Although these models have been quite successful at predicting the formation of binary protostars, a direct comparison between theory and observations has not yet been established. The results of recent observations as well as of early and recent analytic and numerical models, on which the present theory of star formation is based, are reviewed here in a self-consistent manner.

scholarly journals Simulating star formation in molecular cloud cores

2004 ◽  
Vol 414 (2) ◽  
pp. 633-650 ◽  
Author(s):  
S. P. Goodwin ◽  
A. P. Whitworth ◽  
D. Ward-Thompson
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Cloud Cores

The role of magnetic field in the formation and evolution of filamentary molecular clouds

2018 ◽  
Vol 14 (A30) ◽  
pp. 100-100
Author(s):  
Shu-ichiro Inutsuka
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Mass Function ◽  
Convincing Evidence ◽  
Formation And Evolution ◽  
Cloud Cores ◽  
Compressed Layer

AbstractRecent observations have emphasized the importance of the formation and evolution of magnetized filamentary molecular clouds in the process of star formation. Theoretical and observational investigations have provided convincing evidence for the formation of molecular cloud cores by the gravitational fragmentation of filamentary molecular clouds. In this review we summarize our current understanding of various processes that are required in describing the filamentary molecular clouds. Especially we can explain a robust formation mechanism of filamentary molecular clouds in a shock compressed layer, which is in analogy to the making of “Sushi.” We also discuss the origin of the mass function of cores.

scholarly journals Molecular cloud evolution - IV. Magnetic fields, ambipolar diffusion and the star formation efficiency

2011 ◽  
Vol 414 (3) ◽  
pp. 2511-2527 ◽  
Author(s):  
Enrique Vázquez-Semadeni ◽  
Robi Banerjee ◽  
Gilberto C. Gómez ◽  
Patrick Hennebelle ◽  
Dennis Duffin ◽  
...  
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Molecular Cloud ◽  
Ambipolar Diffusion ◽  
Cloud Evolution ◽  
Formation Efficiency

Massive molecular cloud cores and activities of star formation

2005 ◽  
Vol 14 (4) ◽  
pp. 863-868 ◽  
Author(s):  
Zhou Wu-Fei ◽  
Wu Yue-Fang ◽  
Wei Yue ◽  
Ju Bing-Gang
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Cloud Cores
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