Gravitational instability scenario

Cosmology ◽  
2017 ◽  
pp. 109-132
Author(s):  
Nicola Vittorio
Keyword(s):  
Gravitational Instability

Saturation mechanism and generated viscosity in gravito-turbulent accretion disks

2020 ◽  
Vol 640 ◽  
pp. A53
Author(s):  
L. Löhnert ◽  
S. Krätschmer ◽  
A. G. Peeters
Keyword(s):  
Growth Rate ◽  
Numerical Simulations ◽  
Accretion Disks ◽  
Gravitational Instability ◽  
Turbulent Viscosity ◽  
Radial Distance ◽  
Maximum Growth ◽  
Wave Number ◽  
Radiative Cooling ◽  
Mixing Length

Here, we address the turbulent dynamics of the gravitational instability in accretion disks, retaining both radiative cooling and irradiation. Due to radiative cooling, the disk is unstable for all values of the Toomre parameter, and an accurate estimate of the maximum growth rate is derived analytically. A detailed study of the turbulent spectra shows a rapid decay with an azimuthal wave number stronger than ky−3, whereas the spectrum is more broad in the radial direction and shows a scaling in the range kx−3 to kx−2. The radial component of the radial velocity profile consists of a superposition of shocks of different heights, and is similar to that found in Burgers’ turbulence. Assuming saturation occurs through nonlinear wave steepening leading to shock formation, we developed a mixing-length model in which the typical length scale is related to the average radial distance between shocks. Furthermore, since the numerical simulations show that linear drive is necessary in order to sustain turbulence, we used the growth rate of the most unstable mode to estimate the typical timescale. The mixing-length model that was obtained agrees well with numerical simulations. The model gives an analytic expression for the turbulent viscosity as a function of the Toomre parameter and cooling time. It predicts that relevant values of α = 10−3 can be obtained in disks that have a Toomre parameter as high as Q ≈ 10.

scholarly journals N-BODY SIMULATION OF PLANETESIMAL FORMATION THROUGH GRAVITATIONAL INSTABILITY AND COAGULATION. II. ACCRETION MODEL

2009 ◽  
Vol 703 (2) ◽  
pp. 1363-1373 ◽  
Author(s):  
Shugo Michikoshi ◽  
Eiichiro Kokubo ◽  
Shu-ichiro Inutsuka
Keyword(s):  
Gravitational Instability ◽  
Accretion Model

scholarly journals FORMING PLANETESIMALS BY GRAVITATIONAL INSTABILITY. II. HOW DUST SETTLES TO ITS MARGINALLY STABLE STATE

2010 ◽  
Vol 725 (2) ◽  
pp. 1938-1954 ◽  
Author(s):  
Aaron T. Lee ◽  
Eugene Chiang ◽  
Xylar Asay-Davis ◽  
Joseph Barranco
Keyword(s):  
Gravitational Instability ◽  
Stable State

scholarly journals Origin of the prestellar core mass function and link to the IMF – Herschel first results

2010 ◽  
Vol 6 (S270) ◽  
pp. 255-262 ◽  
Author(s):  
Ph. André ◽  
A. Men'shchikov ◽  
V. Könyves ◽  
D. Arzoumanian
Keyword(s):  
Gravitational Instability ◽  
Mass Function ◽  
Initial Mass Function ◽  
Mhd Turbulence ◽  
Core Mass ◽  
Thin Filaments ◽  
Close Relationship ◽  
Prestellar Cores ◽  
First Results ◽  
The Imf

AbstractWe briefly review ground-based (sub)millimeter dust continuum observations of the prestellar core mass function (CMF) and its connection to the stellar initial mass function (IMF). We also summarize the first results obtained on this topic from the Herschel Gould Belt survey, one of the largest key projects with the Herschel Space Observatory. Our early findings with Herschel confirm the existence of a close relationship between the CMF and the IMF. Furthermore, they suggest a scenario according to which the formation of prestellar cores occurs in two main steps: 1) complex networks of long, thin filaments form first, probably as a result of interstellar MHD turbulence; 2) the densest filaments then fragment and develop prestellar cores via gravitational instability.

scholarly journals Star formation thresholds derived From THINGS

2006 ◽  
Vol 2 (S237) ◽  
pp. 397-397
Author(s):  
F. Bigiel ◽  
F. Walter ◽  
E. de Blok ◽  
E. Brinks ◽  
B. Madore
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Gravitational Instability ◽  
Critical Density ◽  
Nearby Galaxy ◽  
Uv Emission ◽  
Radial Profiles ◽  
Wide Range ◽  
First Results ◽  
Type Mass

AbstractWe present first results from THINGS (The HI Nearby Galaxy Survey), which consists of high quality HI maps obtained with the VLA of 34 galaxies across a wide range of galaxy parameters (Hubble type, mass/luminosity). We compare the distribution of HI to the UV emission in our sample galaxies. In particular we present radial profiles of the HI (tracing the neutral interstellar medium) and UV (mainly tracing regions of recent star formation) in our sample galaxies. The azimuthally averaged HI profiles are compared to the predicted critical density above which organized large-scale star formation is believed to start (this threshold is based on the Toomre-Q parameter, which in turn is a measure for local gravitational instability).

scholarly journals GRAVITATIONAL INSTABILITY OF ROTATING, PRESSURE-CONFINED, POLYTROPIC GAS DISKS WITH VERTICAL STRATIFICATION

2012 ◽  
Vol 761 (2) ◽  
pp. 131 ◽  
Author(s):  
Jeong-Gyu Kim ◽  
Woong-Tae Kim ◽  
Young Min Seo ◽  
Seung Soo Hong
Keyword(s):  
Gravitational Instability ◽  
Vertical Stratification ◽  
Polytropic Gas

On gravitational instability of the interstellar gas

1969 ◽  
Vol 5 (1) ◽  
pp. 78-91 ◽  
Author(s):  
Bruno Bertotti ◽  
Alfonso Cavaliere
Keyword(s):  
Gravitational Instability ◽  
Interstellar Gas
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