Razor-thin dust layers in protoplanetary disks: Limits on the vertical shear instability

Abstract

Context: Recent observations with the Atacama Large Millimeter Array (ALMA) have shown that the large dust aggregates observed at millimeter wavelengths settle to the midplane into a remarkably thin layer. Aims: We intend to find out if the geometric thinness of these layers is evidence against the vertical shear instability (VSI) operating in these disks. Methods: We performed hydrodynamic simulations of a protoplanetary disk with a locally isothermal equation of state, and let the VSI fully develop. We sprinkled dust particles and followed their motion as they got stirred up by the VSI. We determined for which grain size the layer becomes geometrically thin enough to be consistent with ALMA observations. We then verified if, with these grain sizes, it is still possible to generate a moderately optically thick layer at millimeter wavelengths, as observations appear to indicate. Results: We found that even very large dust aggregates with Stokes numbers close to unity get stirred up to relatively large heights above the midplane by the VSI, which is in conflict with the observed geometric thinness. For grains so large that the Stokes number exceeds unity, the layer can be made to remain thin, but we show that it is hard to make dust layers optically thick at ALMA wavelengths (e.g., tau(1.3mm)>=1) with such large dust aggregates. Conclusions: We conclude that protoplanetary disks with geometrically thin midplane dust layers cannot be VSI unstable, at least not down to the disk midplane. Explanations for the inhibition of the VSI include a reduced dust-to-gas ratio of the small dust grains that are responsible for the radiative cooling of the disk. A reduction of small grains by a factor of between 10 and 100 is sufficient to quench the VSI. Such a reduction is plausible in dust growth models, and still consistent with observations at optical and infrared wavelengths.

arXiv commentAccepted for publication in Astronomy & Astrophysics

References in corpus (56)

• PLUTO: a Numerical Code for Computational Astrophysics
• First Results from High Angular Resolution ALMA Observations Toward the HL Tau Region
• The Disk Substructures at High Angular Resolution Project (DSHARP): I. Motivation, Sample, Calibration, and Overview
• Using FU Orionis Outbursts to Constrain Self-Regulated Protostellar Disk Models
• Dust coagulation in protoplanetary disks: a rapid depletion of small grains
• Infrared Emission from Interstellar Dust. I. Stochastic Heating of Small Grains
• Gas- and dust evolution in protoplanetary disks
• A Major Asymmetric Dust Trap in a Transition Disk
• Rosseland and Planck Mean Opacities for Protoplanetary Discs
• Flaring vs. self-shadowed disks: the SEDs of Herbig Ae/Be stars
• The Disk Substructures at High Angular Resolution Project (DSHARP): II. Characteristics of Annular Substructures
• Linear and nonlinear evolution of the vertical shear instability in accretion discs
• The effect of dust settling on the appearance of protoplanetary disks
• Dust and Gas in the disc of HL Tauri: Surface density, dust settling, and dust-to-gas ratio
• The Disk Substructures at High Angular Resolution Project (DSHARP): VII. The Planet-Disk Interactions Interpretation
• The Disk Substructures at High Angular Resolution Project (DSHARP) VI: Dust trapping in thin-ringed protoplanetary disks
• Consistent dust and gas models for protoplanetary disks. I. Disk shape, dust settling, opacities, and PAHs
• Trapping dust particles in the outer regions of protoplanetary disks
• Modeling optical properties of cosmic dust grains using a distribution of hollow spheres
• FARGO3D: A new GPU-oriented MHD code
• Radiative transfer in very optically thick circumstellar disks
• Dust Growth and Settling in Protoplanetary Disks and Disk Spectral Energy Distributions. I. Laminar Disks
• Observations of edge-on protoplanetary disks with ALMA I. Results from continuum data
• Measuring turbulent motion in planet-forming disks with ALMA: A detection around DM Tau and non-detections around MWC 480 and V4046 Sgr
• The Eccentric Cavity, Triple Rings, Two-Armed Spirals, and Double Clumps of the MWC 758 Disk
• Cooling Requirements for the Vertical Shear Instability in Protoplanetary Disks
• Dust retention in protoplanetary disks
• Planetesimal formation by the streaming instability in a photoevaporating disk
• Vertical shear instability in accretion disc models with radiation transport
• On the formation of multiple concentric rings and gaps in protoplanetary disks
• A highly settled disk around Oph 163131
• Global MHD simulations of stratified and turbulent protoplanetary discs. II. Dust settling
• Radiation Hydrodynamical Turbulence In Protoplanetary Disks: Numerical Models and Observational Constraints
• Magnetized Accretion and Dead Zones in Protostellar Disks
• Particle dynamics in discs with turbulence generated by the vertical shear instability
• Gas and dust dynamics in starlight-heated protoplanetary disks
• Protoplanetary Disk Rings as Sites for Planetesimal Formation
• The DSHARP Rings: Evidence of Ongoing Planetesimal Formation?
• Estimate on dust scale height from ALMA dust continuum image of the HD 163296 protoplanetary disk
• Mapping the Conditions for Hydrodynamic Instability on Steady State Accretion Models of Protoplanetary Disks
• Dust settling against hydrodynamic turbulence in protoplanetary discs
• How dust fragmentation may be beneficial to planetary growth by pebble accretion
• Efficiency of thermal relaxation by radiative processes in protoplanetary discs: constraints on hydrodynamic turbulence
• On the coexistence of the streaming instability and the vertical shear instability in protoplanetary disks
• Anisotropic hydrodynamic turbulence in accretion disks
• Toroidal vortices and the conglomeration of dust into rings in protoplanetary discs
• Using Ice and Dust Lines to Constrain the Surface Densities of Protoplanetary Disks
• High Resolution Parameter Study of the Vertical Shear Instability
• Zombie Vortex Instability. III. Persistence with Nonuniform Stratification and Radiative Damping
• Importance of radiative effects in gap opening by planets in protoplanetary disks
• Hydrodynamical simulations of protoplanetary disks including irradiation of stellar photons. I. Resolution study for Vertical Shear Instability (VSI)
• Impact of Local Pressure Enhancements on Dust Concentration inTurbulent Protoplanetary Discs
• Effects of Dust Evolution on the Vertical Shear Instability in the Outer Regions of Protoplanetary Disks
• Magnetised Winds in Transition Discs I: 2.5D Global Simulations
• Wavelike nature of the vertical shear instability in global protoplanetary disks
• The saturation of the VSI in protoplanetary disks via parametric instability

Cited by in corpus (19)

• Porous Dust Particles in Protoplanetary Disks: Application to the HL Tau Disk
• Modeling planet-induced gaps and rings in ALMA disks: the role of in-plane radiative diffusion
• Constraining turbulence in protoplanetary discs using the gap contrast: an application to the DSHARP sample
• Dust Coagulation Reconciles Protoplanetary Disk Observations with the Vertical Shear Instability. I. Dust Coagulation and the VSI Dead Zone
• Vertical shear instability in two-moment radiation-hydrodynamical simulations of irradiated protoplanetary disks I. Angular momentum transport and turbulent heating
• Vertical shear instability in two-moment radiation-hydrodynamical simulations of irradiated protoplanetary disks II. Secondary instabilities and stability regions
• Two saturated states of the vertical shear instability in protoplanetary disks with vertically varying cooling times
• Instabilities in dusty non-isothermal proto-planetary discs
• Hydrodynamic turbulence in disks with embedded planets
• Massive Protostellar Disks as a Hot Laboratory of Silicate Grain Evolution
• On the interaction of pebble accreting embryos with the gaseous disc: importance of thermal forces
• Strong clumping in global streaming instability simulations with a dusty fluid
• UV-processing of icy pebbles in the outer parts of VSI-turbulent disks
• Starlight-driven flared-staircase geometry in radiation hydrodynamic models of protoplanetary disks
• Dynamics of small, constant size particles in a protoplanetary disk with an embedded protoplanet
• Measuring the Numerical Viscosity in Simulations of Protoplanetary Disks in Cartesian Grids -- The Viscously Spreading Ring Revisited
• Linear bending wave propagation in laminar and turbulent discs
• How two-dimensional are planet-disc interactions? II. Radiation hydrodynamics and suitable cooling prescriptions
• Hydrodynamical simulations of the vertical shear instability with dynamic dust and cooling rates in protoplanetary disks