<i>N</i>-BODY SIMULATION OF PLANETESIMAL FORMATION THROUGH GRAVITATIONAL INSTABILITY OF A DUST LAYER IN LAMINAR GAS DISK

Michikoshi, Shugo; Kokubo, Eiichiro; Inutsuka, Shu‐ichiro

doi:10.1088/0004-637x/719/2/1021

Cited by 36 publications

(20 citation statements)

References 47 publications

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“…This effectively compares the gravitational shear due to the star acting on a collection of bodies with their own self‐gravity. The Roche density is given by where M * is the stellar mass and a is the semi‐major axis at which the collection of bodies are in orbit (Michikoshi, Kokubo & Inutsuka 2010). Collapse will occur if the local solids density (ρ s ) is greater than the Roche density.…”

Section: Resultsmentioning

confidence: 99%

On the accumulation of planetesimals near disc gaps created by protoplanets

Ayliffe

Laibe

Price

et al. 2012

Monthly Notices of the Royal Astronomical Society

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We have performed three‐dimensional two‐fluid (gas–dust) hydrodynamical models of circumstellar discs with embedded protoplanets (3–333 M⊕) and small solid bodies (radii 10 cm to 10 m). We find that high‐mass planets (≳ Saturn mass) open sufficiently deep gaps in the gas disc such that the density maximum at the outer edge of the gap can very efficiently trap metre‐sized solid bodies. This allows the accumulation of solids at the outer edge of the gap as solids from large radii spiral inwards to the trapping region. This process of accumulation occurs fastest for those bodies that spiral inwards most rapidly, typically metre‐sized boulders, whilst smaller and larger objects will not migrate sufficiently rapidly in the discs lifetime to benefit from the process. Around a Jupiter mass planet we find that bound clumps of solid material, as large as several Earth masses, may form, potentially collapsing under self‐gravity to form planets or planetesimals. These results are in agreement with Lyra et al., supporting their finding that the formation of a second generation of planetesimals or of terrestrial mass planets may be triggered by the presence of a high‐mass planet.

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Section: Resultsmentioning

confidence: 99%

On the accumulation of planetesimals near disc gaps created by protoplanets

Ayliffe

Laibe

Price

et al. 2012

Monthly Notices of the Royal Astronomical Society

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“…On the other hand, the BS10 models do not include the particle's self-gravity, which might help to obtain strong clumping for lower metallicity or higher pressure gradient. This is because with the self-gravity a dust clump is able to collapse even if its initial density is lower than the Roche density (Michikoshi et al 2010). Bai & Stone (2010a,c) reported that their runs saturate within ∼50−100 orbits.…”

Section: Discussionmentioning

confidence: 98%

Can dust coagulation trigger streaming instability?

Drążkowska

Dullemond

2014

A&A

119

115

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Context. Streaming instability can be a very efficient way of overcoming growth and drift barriers to planetesimal formation. However, it was shown that strong clumping, which leads to planetesimal formation, requires a considerable number of large grains. State-ofthe-art streaming instability models do not take into account realistic size distributions resulting from the collisional evolution of dust. Aims. We investigate whether a sufficient quantity of large aggregates can be produced by sticking and what the interplay of dust coagulation and planetesimal formation is. Methods. We develop a semi-analytical prescription of planetesimal formation by streaming instability and implement it in our dust coagulation code based on the Monte Carlo algorithm with the representative particles approach. Results. We find that planetesimal formation by streaming instability may preferentially work outside the snow line, where sticky icy aggregates are present. The efficiency of the process depends strongly on local dust abundance and radial pressure gradient, and requires a super-solar metallicity. If planetesimal formation is possible, the dust coagulation and settling typically need ∼100 orbits to produce sufficiently large and settled grains and planetesimal formation lasts another ∼1000 orbits. We present a simple analytical model that computes the amount of dust that can be turned into planetesimals given the parameters of the disk model.

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“…9 Recent N-body simulations by Michikoshi et al (2010) show that gravitational collapse may occur before Roche density is reached due to the drag force. This is unlikely to affect our conclusion because in the non-clumping case ρp,max is usually more than one order of magnitude smaller than the Roche density, and densest regions are only transient.…”

Section: Formation Of Particle Clumpsmentioning

confidence: 99%

Dynamics of Solids in the Midplane of Protoplanetary Disks: Implications for Planetesimal Formation

Bai

Stone

2010

ApJ

324

375

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We present local two-dimensional (2D) and three-dimensional (3D) hybrid numerical simulations of particles and gas in the midplane of protoplanetary disks (PPDs) using the Athena code. The particles are coupled to gas aerodynamically, with particle-to-gas feedback included. Magnetorotational turbulence is ignored as an approximation for the dead zone of PPDs, and we ignore particle self-gravity to study the precursor of planetesimal formation. Our simulations include a wide size distribution of particles, ranging from strongly coupled particles with dimensionless stopping time τ s ≡ Ωt stop = 10 −4 to marginally coupled ones with τ s = 1 (where Ω is the orbital frequency, t stop is the particle friction time), and a wide range of solid abundances. Our main results are: 1. Particles with τ s 10 −2 actively participate in the streaming instability, generate turbulence and maintain the height of the particle layer before Kelvin-Helmholtz instability is triggered. 2. Strong particle clumping as a consequence of the streaming instability occurs when a substantial fraction of the solids are large (τ s 10 −2 ) and when height-integrated solid to gas mass ratio Z is super-solar. We construct a toy model to offer an explanation. 3. The radial drift velocity is reduced relative to the conventional Nakagawa-Sekiya-Hayashi (NSH) model, especially at high Z. Small particles may drift outward. We derive a generalized NSH equilibrium solution for multiple particle species which fits our results very well. 4. Collision velocity between particles with τ s 10 −2 is dominated by differential radial drift, and is strongly reduced at larger Z. This is also captured by the multi-species NSH solution. Various implications for planetesimal formation are discussed. In particular, we show there exist two positive feedback loops with respect to the enrichment of local disk solid abundance and grain growth. All these effects promote planetesimal formation.

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N-BODY SIMULATION OF PLANETESIMAL FORMATION THROUGH GRAVITATIONAL INSTABILITY OF A DUST LAYER IN LAMINAR GAS DISK

Cited by 36 publications

References 47 publications

On the accumulation of planetesimals near disc gaps created by protoplanets

On the accumulation of planetesimals near disc gaps created by protoplanets

Can dust coagulation trigger streaming instability?

Dynamics of Solids in the Midplane of Protoplanetary Disks: Implications for Planetesimal Formation

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