Planet formation bursts at the borders of the dead zone in 2D numerical simulations of circumstellar disks

被引：0

作者：

Lyra, W. ^{[1
]}

Johansen, A. ^{[2
]}

Zsom, A. ^{[3
]}

Klahr, H. ^{[3
]}

Piskunov, N. ^{[1
]}

机构：

[1] Department of Physics and Astronomy, Uppsala Astronomical Observatory, Box 515, 751 20 Uppsala, Sweden

[2] Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, Netherlands

[3] Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

来源：

Astronomy and Astrophysics | 2009年 / 497卷 / 03期

关键词：

Context. As accretion in protoplanetary disks is enabled by turbulent viscosity; the border between active and inactive (dead) zones constitutes a location where there is an abrupt change in the accretion flow. The gas accumulation that ensues triggers the Rossby wave instability; which in turn saturates into anticyclonic vortices. It has been suggested that the trapping of solids within them leads to a burst of planet formation on very short timescales.Aims. We study in the formation and evolution of the vortices in greater detail; focusing on the implications for the dynamics of embedded solid particles and planet formation.Methods. We performed two-dimensional global simulations of the dynamics of gas and solids in a non-magnetized thin protoplanetary disk with the Pencil code. We used multiple particle species of radius 1; 10; 30; and 100 cm. We computed the particles' gravitational interaction by a particle-mesh method; translating the particles' number density into surface density and computing the corresponding self-gravitational potential via fast Fourier transforms. The dead zone is modeled as a region of low viscosity. Adiabatic and locally isothermal equations of state are used.Results. The Rossby wave instability is triggered under a variety of conditions; thus making vortex formation a robust process. Inside the vortices; fast accumulation of solids occurs and the particles collapse into objects of planetary mass on timescales as short as five orbits. Because the drag force is size-dependent; aerodynamical sorting ensues within the vortical motion; and the first bound structures formed are composed primarily of similarly-sized particles. In addition to erosion due to ram pressure; we identify gas tides from the massive vortices as a disrupting agent of formed protoplanetary embryos. We find evidence that the backreaction of the drag force from the particles onto the gas modifies the evolution of the Rossby wave instability; with vortices being launched only at later times if this term is excluded from the momentum equation. Even though the gas is not initially gravitationally unstable; the vortices can grow to Q ≈ 1 in locally isothermal runs; which halts the inverse cascade of energy towards smaller wavenumbers. As a result; vortices in models without self-gravity tend to rapidly merge towards a m or m = 1 mode; while models with self-gravity retain dominant higher order modes (m = 4 or m =3) for longer times. Non-selfgravitating disks thus show fewer and stronger vortices. We also estimate the collisional velocity history of the particles that compose the most massive embryo by the end of the simulation; finding that the vast majority of them never experienced a collision with another particle at speeds faster than 1 m s-1. This result lends further support to previous studies showing that vortices provide a favorable environment for planet formation.. © 2009 ESO;

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页码：869 / 888