Particle Dynamics in 3D Self-gravitating Disks II: Strong Gas Accretion and Thin Dust Disks

Abstract

Observations suggest that protoplanetary disks have moderate accretion rates onto the central young star, especially at early stages (e.g. HL Tau), indicating moderate disk turbulence. However, recent ALMA observations suggest that dust is highly settled, implying weak turbulence. Motivated by such tension, we carry out 3D stratified local simulations of self-gravitating disks, focusing on settling of dust particles in actively accreting disks. We find that gravitationally unstable disks can have moderately high accretion rates while maintaining a relatively thin dust disk for two reasons. First, accretion stress from the self-gravitating spirals (self-gravity stress) can be stronger than the stress from turbulence (Reynolds stress) by a factor of 5-20. Second, the strong gravity from the gas to the dust decreases the dust scale height by another factor of $\sim 2$. Furthermore, the turbulence is slightly anisotropic, producing a larger Reynolds stress than the vertical dust diffusion coefficient. Thus, gravitoturbulent disks have unusually high vertical Schmidt numbers ($S{c}_z$) if we scale the total accretion stress with the vertical diffusion coefficient (e.g. $S{c}_z\sim$ 10-100). The reduction of the dust scale height by the gas gravity, should also operate in gravitationally stable disks ($Q>$1). Gravitational forces between particles become more relevant for the concentration of intermediate dust sizes, forming dense clouds of dust. After comparing with HL Tau observations, our results suggest that self-gravity and gravity among different disk components could be crucial for solving the conflict between the protoplanetary disk accretion and dust settling, at least at the early stages.

arXiv comment15 pages, 12 figures, Accepted for publication in ApJ

References in corpus (49)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• The NumPy array: a structure for efficient numerical computation
• Nonlinear Outcome of Gravitational Instability in Cooling, Gaseous Disks
• Particle Stirring in Turbulent Gas Disks: Including Orbital Oscillations
• Wind-driven Accretion in Protoplanetary Disks. I: Suppression of the Magnetorotational Instability and Launching of the Magnetocentrifugal Wind
• Linear and nonlinear evolution of the vertical shear instability in accretion discs
• The effect of dust settling on the appearance of protoplanetary disks
• Turbulence in Accretion Disks. Vorticity Generation and Angular Momentum Transport via the Global Baroclinic Instability
• Dust and Gas in the disc of HL Tauri: Surface density, dust settling, and dust-to-gas ratio
• Weak Turbulence in the HD 163296 Protoplanetary Disk Revealed by ALMA CO Observations
• A Three-Dimensional View of Turbulence: Constraints on Turbulent Motions in the HD 163296 Protoplanetary Disk using DCO${}^{+}$
• Protoplanetary disk lifetimes vs stellar mass and possible implications for giant planet populations
• Thanatology in Protoplanetary Discs: the combined influence of Ohmic, Hall, and ambipolar diffusion on dead zones
• Challenges in Forming Planets by Gravitational Instability: Disk Irradiation and Clump Migration, Accretion & Tidal Destructio
• Accelerated planetesimal growth in self-gravitating protoplanetary discs
• The Structure of Spiral Shocks Excited by Planetary-mass Companions
• Characterising the Gravitational Instability in Cooling Accretion Discs
• Hall-effect Controlled Gas Dynamics in Protoplanetary Disks: II. Full 3D Simulations toward the Outer Disk
• Dust diffusion in protoplanetary discs by magnetorotational turbulence
• Observations of edge-on protoplanetary disks with ALMA I. Results from continuum data
• The Radial Distribution of Dust Particles in the HL Tau Disk from ALMA and VLA Observations
• Measuring Turbulence in TW Hya with ALMA: Methods and Limitations
• Convective Overstability in radially stratified accretion disks under thermal relaxation
• Vertical shear instability in accretion disc models with radiation transport
• Radiation Hydrodynamical Turbulence In Protoplanetary Disks: Numerical Models and Observational Constraints
• Turbulence sets the length scale for planetesimal formation: Local 2D simulations of streaming instability and planetesimal formation
• Particle dynamics in discs with turbulence generated by the vertical shear instability
• Numerical convergence in self-gravitating shearing sheet simulations and the stochastic nature of disc fragmentation
• Diffusion and Concentration of Solids in the Dead Zone of a Protoplanetary Disk
• Gas and dust dynamics in starlight-heated protoplanetary disks
• Computational aspects of astrophysical MHD and turbulence
• Dust settling and rings in the outer regions of protoplanetary discs subject to ambipolar diffusion
• Mapping the Conditions for Hydrodynamic Instability on Steady State Accretion Models of Protoplanetary Disks
• Planetesimal Formation In Self-Gravitating Discs
• Efficiency of thermal relaxation by radiative processes in protoplanetary discs: constraints on hydrodynamic turbulence
• Vortex Formation and Survival in Protoplanetary Disks subject to Vertical Shear Instability
• Requirements for gravitational collapse in planetesimal formation --- the impact of scales set by Kelvin-Helmholtz and nonlinear streaming instability
• Modeling protoplanetary disk SEDs with artificial neural networks: Revisiting the viscous disk model and updated disk masses
• Spatially Extended Brackett Gamma Emission in the Environments of Young Stars
• Collision velocity of dust grains in self-gravitating protoplanetary discs
• Gravito-Turbulent Disks in 3D: Turbulent Velocities vs. Depth
• Magnetically Induced Disk Winds and Transport in the HL Tau Disk
• The properties of the inner disk around HL Tau: Multi-wavelength modeling of the dust emission
• Gravito-turbulence and the excitation of small-scale parametric instability in astrophysical discs
• Characterizing gravito-turbulence in 3D: turbulent properties and stability against fragmentation
• Dust dynamics and vertical settling in gravitoturbulent protoplanetary discs
• Particle Dynamics in 3D Self-gravitating Disks I: Spirals
• Spiral density waves and vertical circulation in protoplanetary discs
• Dust Growth and Dynamics in Protoplanetary Nebulae: Implications for Opacity, Thermal Profile and Gravitational Instability

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• Filling in the Gaps: Can Gravitationally Unstable Discs Form the Seeds of Gas Giant Planets?
• Distinguishing Magnetized Disc Winds from Turbulent Viscosity through Substructure Morphology in Planet-forming Discs
• The steady-state hydrodynamics of a long-lived disc: planetary system architecture and prospects of observing a circumplanetary disc shadow in V4046Sgr
• Massive Protostellar Disks as a Hot Laboratory of Silicate Grain Evolution
• Turbulent Transport of Dust Particles in Protostellar Disks: The Effect of Upstream Diffusion
• Primordial dust rings, hidden dust mass, and the first generation of planetesimals in gravitationally unstable protoplanetary disks
• Self-gravity in thin-disc simulations of protoplanetary discs: smoothing length rectified and generalised to bi-fluids
• Gravito-turbulent bi-fluid protoplanetary discs: 1. An analytical perspective to stratification
• An efficient spectral Poisson solver for the nirvana-III code: the shearing-box case with vertical vacuum boundary conditions
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