A low accretion efficiency of planetesimals formed at planetary gap edges

Abstract

Observations and models of giant planets indicate that such objects are enriched in heavy elements compared to solar abundances. The prevailing view is that giant planets accreted multiple Earth masses of heavy elements after the end of core formation. Such late solid enrichment is commonly explained by the accretion of planetesimals. Planetesimals are expected to form at the edges of planetary gaps, and here we address the question of whether these planetesimals can be accreted in large enough amounts to explain the inferred high heavy element contents of giant planets. We perform a series of N-body simulations of the dynamics of planetesimals and planets during the planetary growth phase, taking into account gas drag as well as the enhanced collision cross-section caused by the extended envelopes. We consider the growth of Jupiter and Saturn via gas accretion after reaching the pebble isolation mass and we include their migration in an evolving disk. We find that the accretion efficiency of planetesimals formed at planetary gap edges is very low: less than 10% of the formed planetesimals are accreted even in the most favorable cases, which in our model corresponds to a few Earth-masses. When planetesimals are assumed to form beyond the feeding zone of the planets, extending to a few Hill radii from a planet, accretion becomes negligible. Furthermore, we find that the accretion efficiency increases when the planetary migration distance is increased and that the efficiency does not increase when the planetesimal radii are decreased. Based on these results we conclude that it is difficult to explain the large heavy element content of giant planets with planetesimal accretion during the gas accretion phase. Alternative processes most likely are required, e.g. accretion of vapor deposited by drifting pebbles.

arXiv commentAccepted for publication in A&A

References in corpus (46)

• Spectral Energy Distributions of T Tauri Stars With Passive Circumstellar Disks
• Streaming Instabilities in Protoplanetary Disks
• REBOUND: An open-source multi-purpose N-body code for collisional dynamics
• Asteroids Were Born Big
• Separating gas-giant and ice-giant planets by halting pebble accretion
• The Mass-Metallicity Relation for Giant Planets
• Particle Clumping and Planetesimal Formation Depend Strongly on Metallicity
• Comparing Jupiter interior structure models to Juno gravity measurements and the role of a dilute core
• Dynamics of Solids in the Midplane of Protoplanetary Disks: Implications for Planetesimal Formation
• A correlation between the heavy element content of transiting extrasolar planets and the metallicity of their parent stars
• Pebble isolation mass --- scaling law and implications for the formation of super-Earths and gas giants
• Concentrating small particles in protoplanetary disks through the streaming instability
• Gas Flow Across Gaps in Protoplanetary Disks
• How to form planetesimals from mm-sized chondrules and chondrule aggregates
• The great dichotomy of the Solar System: small terrestrial embryos and massive giant planet cores
• The Heavy Element Masses of Extrasolar Giant Planets, Revealed
• Three-dimensional simulations of multiple protoplanets embedded in a protostellar disc
• Chemical enrichment of giant planets and discs due to pebble drift
• Radial migration of gap-opening planets in protoplanetary disks. I. The case of a single planet
• On the Minimum Core Mass for Giant Planet Formation at Wide Separations
• Atmospheric Signatures of Giant Exoplanet Formation by Pebble Accretion
• How drifting and evaporating pebbles shape giant planets I: Heavy element content and atmospheric C/O
• Standing on the shoulders of giants: Trojan Earths and vortex trapping in low mass self-gravitating protoplanetary disks of gas and solids
• Planet formation with envelope enrichment: new insights on planetary diversity
• Hybrid Symplectic Integrators for Planetary Dynamics
• Final Masses of Giant Planets II: Jupiter Formation in a Gas-Depleted Disk
• How planetary growth outperforms migration
• The formation of Jupiter by hybrid pebble-planetesimal accretion
• The Formation of Jupiter's Diluted Core by a Giant Impact
• How drifting and evaporating pebbles shape giant planets II: Volatiles and refractories in atmospheres
• Protoplanetary Disk Rings as Sites for Planetesimal Formation
• The DSHARP Rings: Evidence of Ongoing Planetesimal Formation?
• Interior Models of Saturn: Including the Uncertainties in Shape and Rotation
• The origin of the high metallicity of close-in giant exoplanets: Combined effect of the resonant and aerodynamic shepherding
• Infall of planetesimals onto growing giant planets: onset of runaway gas accretion and metallicity of their gas envelopes
• Jupiter's heavy-element enrichment expected from formation models
• Giant planet formation models with a self-consistent treatment of the heavy elements
• Rapid formation of Gas Giant Planets via Collisional Coagulation from Dust Grains to Planetary Cores
• Pebble drift and planetesimal formation in protoplanetary discs with embedded planets
• The properties of heavy elements in giant planet envelopes
• Embryo impacts and gas giant mergers I: Dichotomy of Jupiter and Saturn's core mass
• The fate of planetesimals formed at planetary gap edges
• Enrichment of Jupiter's atmosphere by late planetesimal bombardment
• The origin of the high metallicity of close-in giant exoplanets II The nature of the sweet spot for accretion
• The Interiors of Jupiter and Saturn
• An Approximation for the Capture Radius of Gaseous Protoplanets

Cited by in corpus (6)

• Breaking Degeneracies in Formation Histories by Measuring Refractory Content in Gas Giants
• Revising the Giant Planet Mass-Metallicity Relation: Deciphering the Formation Sequence of Giant Planets
• Formation of wide-orbit giant planets in protoplanetary disks with a decreasing pebble flux
• Growth after the streaming instability: The radial distance dependence of the planetary growth
• Heavy-element Accretion by Proto-Jupiter in a Massive Planetesimal Disk, Revisited
• There is no disk mass budget problem of planet formation