Turbulent Disk Viscosity and the Bifurcation of Planet Formation Histories

Abstract

ALMA observations of dust ring/gap structures in a minority but growing sample of protoplanetary disks can be explained by the presence of planets at large disk radii - yet the origins of these planets remains debated. We perform planet formation simulations using a semi-analytic model of the HL Tau disk to follow the growth and migration of hundreds of planetary embryos initially distributed throughout the disk, assuming either a high or low turbulent $\alpha$ viscosity. We have discovered that there is a bifurcation in the migration history of forming planets as a consequence of varying the disk viscosity. In our high viscosity disks, inward migration prevails and yields compact planetary systems, tempered only by planet trapping at the water iceline around 5 au. In our lower viscosity models however, low mass planets can migrate outward to twice their initial orbital radii, driven by a radially extended region of strong outward-directed corotation torques located near the heat transition (where radiative heating of the disk by the star is comparable to viscous heating) - before eventually migrating inwards. We derive analytic expressions for the planet mass at which the corotation torque dominates, and find that this "corotation mass" scales as $M_{\mathrm{p},\mathrm{corot}}\sim {\alpha }^{2/3}$. If disk winds dominate the corotation torque, the corotation mass scales linearly with wind strength. We propose that the observed bifurcation in disk demographics into a majority of compact dust disks and a minority of extended ring/gap systems is a consequence of a distribution of viscosity across the disk population.

25 pages, 15 figures, 10 movies (links embedded). Published in MNRAS

References in corpus (46)

• Gas- and dust evolution in protoplanetary disks
• Two accreting protoplanets around the young star PDS 70
• Toward a Deterministic Model of Planetary Formation V. Accumulation Near the Ice Line
• The imprint of exoplanet formation history on observable present-day spectra of hot Jupiters
• Asymmetric features in the protoplanetary disk MWC758
• Global simulations of protoplanetary disks with ohmic resistivity and ambipolar diffusion
• A Three-Dimensional View of Turbulence: Constraints on Turbulent Motions in the HD 163296 Protoplanetary Disk using DCO${}^{+}$
• Hints for a Turnover at the Snow Line in the Giant Planet Occurrence Rate
• On the corotation torque in a radiatively inefficient disk
• Meridional flows in the disk around a young star
• Dust flow in gas disks in the presence of embedded planets
• Initial mass function of planetesimals formed by the streaming instability
• On the formation of planetary systems via oligarchic growth in thermally evolving viscous discs
• Measuring turbulent motion in planet-forming disks with ALMA: A detection around DM Tau and non-detections around MWC 480 and V4046 Sgr
• On corotation torques, horseshoe drag and the possibility of sustained stalled or outward protoplanetary migration
• On disc protoplanet interactions in a non-barotropic disc with thermal diffusion
• ALMA discovery of a rotating SO/SO${}_2$ flow in HH212. A possible MHD disk wind?
• Grain opacity and the bulk composition of extrasolar planets. II. An analytical model for the grain opacity in protoplanetary atmospheres
• Composition of Early Planetary Atmospheres I: Connecting Disk Astrochemistry to the Formation of Planetary Atmospheres
• A stellar mass dependence of structured disks: a possible link with exoplanet demographics
• The Role of Magnetic Fields in Protostellar Outflows and Star Formation
• Connecting planet formation and astrochemistry: A main sequence for C/O in hot-exoplanetary atmospheres
• Protoplanetary Disk Rings as Sites for Planetesimal Formation
• On the gap-opening criterion of migrating planets in protoplanetary disks
• Observed sizes of planet-forming disks trace viscous evolution
• Estimate on dust scale height from ALMA dust continuum image of the HD 163296 protoplanetary disk
• Bridging the gap between protoplanetary and debris disks: separate evolution of millimeter and micrometer-sized dust
• Global Hydromagnetic Simulations of Protoplanetary Disks with Stellar Irradiation and Simplified Thermochemistry
• On the width and shape of the corotation region for low-mass planets
• Connecting planet formation and astrochemistry: Refractory carbon depletion leading to super-stellar C/O in giant planetary atmospheres
• Constraining MHD disk winds with ALMA. Apparent rotation signatures and application to HH212
• Growing and Trapping Pebbles with Fragile Collisions of Particles in Protoplanetary Disks
• A Multi-Epoch HST Study of the Herbig-Haro Flow from XZ Tauri
• Effect of wind-driven accretion on planetary migration
• 13C17O suggests gravitational instability in the HL Tau disc
• Exploring the conditions for forming cold gas giants through planetesimal accretion
• Magnetically Induced Disk Winds and Transport in the HL Tau Disk
• Low-mass planet migration in three dimensional wind-driven inviscid discs: a negative corotation torque
• Investigating the Relative Gas and Small Dust Grain Surface Heights in Protoplanetary Disks
• Outward Migration of Super-Jupiters
• Impact of Differential Dust Settling on the SED and Polarization: Application to the Inner Region of the HL Tau Disk
• Survival of ALMA Rings in the Absence of Pressure Maxima
• Physics of Planet Trapping with Applications to HL Tau
• Promoted Mass Growth of Multiple, Distant Giant Planets through Pebble Accretion and Planet-Planet Collision
• Formation of Planetary Populations II: Effects of Initial Disk Size & Radial Dust Drift
• Super-Earths as Failed Cores in Orbital Migration Traps

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