Dust trapping by vortices in transitional disks: Evidence for non-ideal magnetohydrodynamic effects in protoplanetary disks

Zhaohuan Zhu, James McLellan Stone

Research output: Contribution to journalArticle

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Abstract

We study particle trapping at the edge of a gap opened by a planet in a protoplanetary disk. In particular, we explore the effects of turbulence driven by the magnetorotational instability on particle trapping, using global three-dimensional magnetohydrodynamic (MHD) simulations including Lagrangian dust particles. We study disks either in the ideal MHD limit or dominated by ambipolar diffusion (AD) which plays an essential role at the outer regions of a protoplanetary disk. With ideal MHD, strong turbulence (the equivalent viscosity parameter α ∼ 10-2) in disks prevents vortex formation at the edge of the gap opened by a 9 MJ planet, and most particles (except the particles that drift fastest) pile up at the outer gap edge almost axisymmetrically. When AD is considered, turbulence is significantly suppressed (α ≲ 10-3), and a large vortex forms at the edge of the planet induced gap, which survives ∼1000 orbits. The vortex can efficiently trap dust particles that span 3 orders of magnitude in size within 100 planetary orbits. We have also carried out two-dimensional hydrodynamical (HD) simulations using viscosity as an approximation to MHD turbulence. These HD simulations can reproduce vortex generation at the gap edge as seen in MHD simulations. Finally, we use our simulation results to generate synthetic images for ALMA dust continuum observations on Oph IRS 48 and HD 142527, which show good agreement with existing observations. Predictions for future ALMA cycle 2 observations have been made. We conclude that the asymmetry in ALMA observations can be explained by dust trapping vortices and the existence of vortices could be the evidence that the outer protoplanetary disks are dominated by AD with α < 10-3 at the disk midplane.

Original languageEnglish (US)
Article number53
JournalAstrophysical Journal
Volume795
Issue number1
DOIs
StatePublished - Nov 1 2014

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • accretion, accretion disks
  • astroparticle physics
  • magnetohydrodynamics (MHD)
  • planetdisk interaction
  • stars: individual (Oph IRS 48, HD 142527)
  • turbulence

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