scholarly journals Non-linear development of secular gravitational instability in protoplanetary disks

2018 ◽  
Vol 70 (1) ◽  
Author(s):  
Ryosuke T Tominaga ◽  
Shu-ichiro Inutsuka ◽  
Sanemichi Z Takahashi
Keyword(s):  
Gravitational Instability ◽  
Protoplanetary Disks ◽  
Non Linear

scholarly journals The Formation of Galaxies in Friedmannian Universes

1974 ◽  
Vol 63 ◽  
pp. 213-225 ◽  
Author(s):  
A. G. Doroshkevich ◽  
R. A. Sunyaev ◽  
Ya. B. Zel'Dovich
Keyword(s):  
Linear Theory ◽  
Initial Conditions ◽  
Gravitational Instability ◽  
Short Review ◽  
Clusters Of Galaxies ◽  
Non Linear

A short review of the theory of the formation of galaxies and clusters of galaxies is given within the framework of the non-linear theory of gravitational instability. Probable initial conditions are discussed as well as processes which bring about the origin of galaxies and clusters of galaxies. Possible observational tests are discussed.

scholarly journals Gravitoviscous protoplanetary disks with a dust component

2019 ◽  
Vol 631 ◽  
pp. A1 ◽  
Author(s):  
Eduard I. Vorobyov ◽  
Vardan G. Elbakyan
Keyword(s):  
Gravitational Instability ◽  
Protoplanetary Disks ◽  
Maximum Radius ◽  
Order Of Magnitude ◽  
Dust Component ◽  
Tidal Torques ◽  
Self Gravity ◽  
Small Dust ◽  
Collapse Phase ◽  
Hydrodynamics Equations

Aims. Spatial distribution and growth of dust in a clumpy protoplanetary disk subject to vigorous gravitational instability and fragmentation is studied numerically with sub-au resolution using the FEOSAD code. Methods. Hydrodynamics equations describing the evolution of self-gravitating and viscous protoplanetary disks in the thin-disk limit were modified to include a dust component consisting of two parts: sub-micron-sized dust and grown dust with a variable maximum radius. The conversion of small to grown dust, dust growth, friction of dust with gas, and dust self-gravity were also considered. Results. We found that the disk appearance is notably time-variable with spiral arms, dusty rings, and clumps, constantly forming, evolving, and decaying. As a consequence, the total dust-to-gas mass ratio is highly non-homogeneous throughout the disk extent, showing order-of-magnitude local deviations from the canonical 1:100 value. Gravitationally bound clumps formed through gravitational fragmentation have a velocity pattern that deviates notably from the Keplerian rotation. Small dust is efficiently converted into grown dust in the clump interiors, reaching a maximum radius of several decimeters. Concurrently, grown dust drifts towards the clump center forming a massive compact central condensation (70–100 M⊕). We argue that protoplanets may form in the interiors of inward-migrating clumps before they disperse through the action of tidal torques. We foresee the formation of protoplanets at orbital distances of several tens of au with initial masses of gas and dust in the protoplanetary seed in the (0.25–1.6) MJup and (1.0–5.5) M⊕ limits, respectively. The final masses of gas and dust in the protoplanets may however be much higher due to accretion from surrounding massive metal-rich disks/envelopes. Conclusions. Dusty rings formed through tidal dispersal of inward-migrating clumps may have a connection to ring-like structures found in youngest and massive protoplanetary disks. Numerical disk models with a dust component that can follow the evolution of gravitationally bound clumps through their collapse phase to the formation of protoplanets are needed to make firm conclusions on the characteristics of planets forming through gravitational fragmentation.

scholarly journals On the non-axisymmetric fragmentation of rings generated by the Secular Gravitational Instability

2021 ◽  
Author(s):  
Arnaud Pierens
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Linear Growth ◽  
Gravitational Instability ◽  
Dust Particles ◽  
Linear Growth Rate ◽  
Stability Parameters ◽  
Dust Density ◽  
Linear Evolution ◽  
Non Linear

Abstract Ringed structures have been observed in a variety of protoplanetary discs. Among the processes that might be able to generate such features, the Secular Gravitational Instability (SGI) is a possible candidate. It has also been proposed that the SGI might lead to the formation of planetesimals during the non-linear phase of the instability. In this context, we employ two-fluid hydrodynamical simulations with self-gravity to study the non-axisymmetric, non-linear evolution of ringed perturbations that grow under the action of the SGI. We find that the non-linear evolution outcome of the SGI depends mainly on the initial linear growth rate. For SGI growth rates smaller than typically σ ≳ 10−4 − 10−5Ω, dissipation resulting from dust feedback introduces a m = 1 spiral wave in the gas, even for Toomre gas stability parameters Qg > 2 for which non-axisymmetric instabilities appear in a purely gaseous disc. This one-armed spiral subsequently traps dust particles until a dust-to-gas ratio ε ∼ 1 is achieved. For higher linear growth rates, the dust ring is found to undergo gravitational collapse until the bump in the surface density profile becomes strong enough to trigger the formation of dusty vortices through the Rossby Wave Instability (RWI). Enhancements in dust density resulting from this process are found to scale with the linear growth rate, and can be such that the dust density is higher than the Roche density, leading to the formation of bound clumps. Fragmentation of axisymmetric rings produced by the SGI might therefore appear as a possible process for the formation of planetesimals.

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