Fast Modes and Dusty Horseshoes in Transitional Disks

Abstract

The brightest transitional protoplanetary disks are often azimuthally asymmetric: their mm-wave thermal emission peaks strongly on one side. Dust overdensities can exceed $\sim$100:1, while gas densities vary by factors less than a few. We propose that these remarkable ALMA observations---which may bear on how planetesimals form---reflect a gravitational global mode in the gas disk. The mode is (1) fast---its pattern speed equals the disk's mean Keplerian frequency; (2) of azimuthal wavenumber $m=1$, displacing the host star from the barycenter; and (3) Toomre-stable. We solve for gas streamlines including the indirect stellar potential in the frame rotating with the pattern speed, under the drastic simplification that gas does not feel its own gravity. Near co-rotation, the gas disk takes the form of a horseshoe-shaped annulus. Dust particles with aerodynamic stopping times much shorter or much longer than the orbital period are dragged by gas toward the horseshoe center. For intermediate stopping times, dust converges toward a $\sim$45${}^{\circ }$-wide arc on the co-rotation circle. Particles that do not reach their final accumulation points within disk lifetimes, either because of gas turbulence or long particle drift times, conform to horseshoe-shaped gas streamlines. Our mode is not self-consistent because we neglect gas self-gravity; still, we expect that trends between accumulation location and particle size, similar to those we have found, are generically predicted by fast modes and are potentially observable. Unlike vortices, global modes are not restricted in radial width to the pressure scale height; their large radial and azimuthal extents may better match observations.

arXiv commentAccepted to ApJ Letters

References in corpus (23)

• PLUTO: a Numerical Code for Computational Astrophysics
• Particle Stirring in Turbulent Gas Disks: Including Orbital Oscillations
• A Major Asymmetric Dust Trap in a Transition Disk
• Observations of gas flows inside a protoplanetary gap
• Large-Scale Asymmetries in the Transitional Disks of SAO 206462 and SR 21
• LkH$\alpha$ 330: Evidence for dust clearing through resolved submillimeter imaging
• Evidence for dust clearing through resolved submillimeter imaging
• Steady state of dust distributions in disk vortices: Observational predictions and applications to transitional disks
• Local Enhancement of Surface Density in the Protoplanetary Ring Surrounding HD 142527
• An azimuthal asymmetry in the LkHa 330 disk
• Gas structure inside dust cavities of transition disks: Oph IRS 48 observed by ALMA
• Dust Trapping by Vortices in Transitional Disks: Evidence for Non-ideal MHD Effects in Protoplanetary Disks
• Simulations of dust-trapping vortices in protoplanetary discs
• The circumstellar disk of AB Aurigae: evidence for envelope accretion at late stages of star formation?
• CO gas inside the protoplanetary disk cavity in HD 142527: disk structure from ALMA
• Slow modes in Keplerian disks
• Rossby Wave Instability in three dimensional discs
• The effect of self-gravity on vortex instabilities in disc-planet interactions
• Edge modes in self-gravitating disc-planet interactions
• The Origin of the Young Stars in the Nucleus of M31
• Formation, Survival, and Destruction of Vortices in Accretion Disks
• Density waves in debris discs and galactic nuclei
• Global m=1 instabilities and lopsidedness in disc galaxies

Cited by in corpus (32)

• The Eccentric Cavity, Triple Rings, Two-Armed Spirals, and Double Clumps of the MWC 758 Disk
• Evidence for a massive dust-trapping vortex connected to spirals: a multi-wavelength analysis of the HD~135344B protoplanetary disk
• A compact concentration of large grains in the HD142527 protoplanetary dust trap
• Spiral Arms in Gravitationally Unstable Protoplanetary Disks as Imaged in Scattered Light
• A Close-up View of the Young Circumbinary Disk HD 142527
• Gas and dust hydrodynamical simulations of massive lopsided transition discs - II. Dust concentration
• Observations of Solids in Protoplanetary Disks
• High-Resolution ALMA Observations of HD100546: Asymmetric Circumstellar Ring, and Circumplanetary Disk Upper Limits
• Parametric Study of the Rossby Wave Instability in a Two-Dimensional Barotropic Disk
• Gas and dust hydrodynamical simulations of massive lopsided transition discs - I. Gas distribution
• A dusty filament and turbulent CO spirals in HD135344B-SAO206462
• Dust capture and long-lived density enhancements triggered by vortices in 2D protoplanetary disks
• An Analytic Criterion for Turbulent Disruption of Planetary Resonances
• Compact dust concentration in the MWC 758 protoplanetary disk
• Long-Lived Dust Asymmetries at Dead Zone Edges in Protoplanetary Disks
• Stability and Occurrence Rate Constraints on the Planetary Sculpting Hypothesis for "Transitional" Disks
• Significant Gas-to-Dust Ratio Asymmetry and Variation in the Disk of HD 142527 and the Indication of Gas Depletion
• Vortex-like kinematic signal, spirals, and beam smearing effect in the HD 142527 disk
• Cm-wavelength observations of MWC758: resolved dust trapping in a vortex
• Observational Signatures of Planets in Protoplanetary Disks: Planet-Induced Line Broadening in Gaps
• Extreme Asymmetry in the Disk of V1247 Ori
• The circumstellar disk response to the motion of the host star
• Resolved observations of transition disks
• Interpreting Brightness Asymmetries in Transition Disks: Vortex at Dead Zone or Planet Carved Gap Edges?
• Long-Lived Eccentricities in Accretion Disks
• Detailed modeling of dust distribution in the disk of HD 142527
• Extreme Pebble Accretion in Ringed Protoplanetary Discs
• On the vortex evolution in non-isothermal protoplanetary discs
• On the evolution of vortex in locally isothermal self-gravitating discs: a parameter study
• Morphology and dynamical stability of self-gravitating vortices: Numerical simulations
• Planetary nurseries: vortices formed at smooth viscosity transition
• Indirect forces in disc-planet interaction