The Heavy-element Content Trend of Planets: A Tracer of their Formation Sites

Abstract

Identification of the main planet formation site is fundamental to understanding how planets form and migrate to the current locations. We consider the heavy-element content trend of observed exoplanets derived from improved measurements of mass and radius, and explore how this trend can be used as a tracer of their formation sites. Using gas accretion recipes obtained from detailed hydrodynamical simulations, we confirm that the disk-limited gas accretion regime is most important for reproducing the heavy-element content trend. Given that such a regime is specified by two characteristic masses of planets, we compute these masses as a function of the distance ($r$) from the central star, and then examine how the regime appears in the mass-semimajor axis diagram. Our results show that a plausible solid accretion region emerges at $r\simeq 0.6$ au and expands with increasing $r$, using the conventional disk model. Given that exoplanets that possess the heavy-element content trend distribute currently near their central stars, our results imply the importance of planetary migration that would occur after solid accretion onto planets might be nearly completed at $r\ge 0.6$ au. Self-consistent simulations would be needed to verify the predictions herein.

6 pages, 3 figures, accepted for publication in ApJ Letters

References in corpus (15)

• Comparing Jupiter interior structure models to Juno gravity measurements and the role of a dilute core
• The imprint of exoplanet formation history on observable present-day spectra of hot Jupiters
• Models of the in situ formation of detected extrasolar giant planets
• Towards Chemical Constraints on Hot Jupiter Migration
• Formation of Jupiter using opacities based on detailed grain physics
• Mass Estimates of a Giant Planet in a Protoplanetary Disk from the Gap Structures
• An Atmospheric Structure Equation for Grain Growth
• Planetesimal Accretion onto Growing Proto-Gas-Giant Planets
• Grain opacity and the bulk composition of extrasolar planets. I. Results from scaling the ISM opacity
• A Systematic Study of the Final Masses of Gas Giant Planets
• C/O and O/H Ratios Suggest Some Hot Jupiters Originate Beyond the Snow Line
• Infall of planetesimals onto growing giant planets: onset of runaway gas accretion and metallicity of their gas envelopes
• Planet Traps and Planetary Cores: Origins of the Planet-Metallicity Correlation
• Magnetically Induced Disk Winds and Transport in the HL Tau Disk
• Super-Earths as Failed Cores in Orbital Migration Traps

Cited by in corpus (5)

• SimAb: A simple, fast and flexible model to assess the effects of planet formation on the atmospheric composition of gas giants
• Formation of Planetary Populations II: Effects of Initial Disk Size & Radial Dust Drift
• Heavy-element Accretion by Proto-Jupiter in a Massive Planetesimal Disk, Revisited
• Magnetic Fields and Accreting Giant Planets around PDS 70
• Solid Accretion onto Neptune-Mass Planets I: In-Situ Accretion and Constraints from the metallicity of Uranus and Neptune