Dead Zones as Thermal Barriers to Rapid Planetary Migration in Protoplanetary Disks

Abstract

Planetary migration in standard models of gaseous protoplanetary disks is known to be very rapid ($\sim 10^5$ years) jeopardizing the existence of planetary systems. We present a new mechanism for significantly slowing rapid planetary migration, discovered by means of radiative transfer calculations of the thermal structure of protoplanetary disks irradiated by their central stars. Rapid dust settling in a disk's dead zone - a region with very little turbulence - leaves a dusty wall at its outer edge. We show that the back-heating of the dead zone by this irradiated wall produces a positive gradient of the disk temperature which acts as a thermal barrier to planetary migration which persists for the disk lifetime. Although we analyze in detail the migration of a Super-Earth in a low mass disk around an M star, our findings can apply to wide variety of young planetary systems. We compare our findings with other potentially important stopping mechanisms and show that there are large parameter spaces for which dead zones are likely to play the most important role for reproducing the observed mass-period relation in longer planetary periods.

19 pages, 3 figures, 1 table, accepted for publication in ApJ Letters

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• Planet gaps in the dust layer of 3D protoplanetary disks: I. Hydrodynamical simulations of T Tauri disks
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• Evolutionary Tracks of Trapped, Accreting Protoplanets: the Origin of the Observed Mass-Period Relation
• Do Giant Planets Survive Type II Migration?
• Outward migration of a super-Earth in a disc with outward propagating density waves excited by a giant planet
• Corotation torques experienced by planets embedded in weakly magnetized turbulent discs
• Planet Traps and Planetary Cores: Origins of the Planet-Metallicity Correlation
• Recent developments in planet migration theory
• On the Formation and Chemical Composition of Super Earths
• The formation of the Galilean moons and Titan in the Grand Tack scenario
• Planet Traps and First Planets: the Critical Metallicity for Gas Giant Formation
• Dust Settling and Rapid Planetary Migration
• Formation of Planetary Populations I: Metallicity & Envelope Opacity Effects
• Formation of hot Jupiters through disk migration and evolving stellar tides
• Chondrule Formation via Impact Jetting Triggered by Planetary Accretion
• Migration and Growth of Protoplanetary Embryos III: Mass and Metallicity Dependence for FGKM main-sequence stars
• Physics of Planet Trapping with Applications to HL Tau
• Formation of Planetary Populations II: Effects of Initial Disk Size & Radial Dust Drift
• Super-Earths as Failed Cores in Orbital Migration Traps
• Combined Effects of Disk Winds and Turbulence-Driven Accretion on Planet Populations
• Callisto's Nonresonant Orbit as an Outcome of Circum-Jovian Disk Substructure
• Dead Zones and the Diversity of Exoplanetary Systems
• Dynamical Evolution of Planetary Systems
• Disk Inhomogeneities and the Origins of Planetary System Architectures and Observational Properties