Formation of Planetary Populations III: Core Composition & Atmospheric Evaporation

Abstract

The exoplanet mass radius diagram reveals that super Earths display a wide range of radii, and therefore mean densities, at a given mass. Using planet population synthesis models, we explore the key physical factors that shape this distribution: planets' solid core compositions, and their atmospheric structure. For the former, we use equilibrium disk chemistry models to track accreted minerals onto planetary cores throughout formation. For the latter, we track gas accretion during formation, and consider photoevaporation-driven atmospheric mass loss to determine what portion of accreted gas escapes after the disk phase. We find that atmospheric stripping of Neptunes and sub-Saturns at small orbital radii ($\lesssim$0.1AU) plays a key role in the formation of short-period super Earths. Core compositions are strongly influenced by the trap in which they formed. We also find a separation between Earth-like planet compositions at small orbital radii $\lesssim$0.5AU and ice-rich planets (up to 50\% by mass) at larger orbits $\sim$1AU. This corresponds well with the Earth-like mean densities inferred from the observed position of the low-mass planet radius valley at small orbital periods. Our model produces planet radii comparable to observations at masses $\sim$1-3M${}_{\oplus }$. At larger masses, planets' accreted gas significantly increases their radii to be larger than most of the observed data. While photoevaporation, affecting planets at small orbital radii $\lesssim$0.1AU, reduces a subset of these planets' radii and improves our comparison, most planets in our computed populations are unaffected due to low FUV fluxes as they form at larger separations.

arXiv comment28 pages, 16 figures, accepted for publication in MNRAS

References in corpus (90)

• The chemical composition of the Sun
• First Results from High Angular Resolution ALMA Observations Toward the HL Tau Region
• Planet Occurrence within 0.25 AU of Solar-type Stars from Kepler
• The Disk Substructures at High Angular Resolution Project (DSHARP): I. Motivation, Sample, Calibration, and Overview
• Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data
• Characteristics of planetary candidates observed by Kepler, II: Analysis of the first four months of data
• The Keck Planet Search: Detectability and the Minimum Mass and Orbital Period Distribution of Extrasolar Planets
• A simple model for the evolution of the dust population in protoplanetary disks
• Evolution of the Solar Activity over Time and Effects on Planetary Atmospheres: I. High-energy Irradiances (1-1700 A)
• Mass-Radius Relationships for Solid Exoplanets
• Kepler planets: a tale of evaporation
• Most 1.6 Earth-Radius Planets are not Rocky
• Atmospheric Escape from Hot Jupiters
• Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70
• Habitable Zones Around Main-Sequence Stars: Dependence on Planetary Mass
• Gas- and dust evolution in protoplanetary disks
• Probabilistic Forecasting of the Masses and Radii of Other Worlds
• The Spitzer ice legacy: Ice evolution from cores to protostars
• The formation and retention of gas giant planets around stars with a range of metallicities
• On the radiative equilibrium of irradiated planetary atmospheres
• Internal Structure of Massive Terrestrial Planets
• Extrasolar planet population synthesis I: Method, formation tracks and mass-distance distribution
• Wind-driven Accretion in Protoplanetary Disks. I: Suppression of the Magnetorotational Instability and Launching of the Magnetocentrifugal Wind
• Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems
• The Role of Core Mass in Controlling Evaporation: the Kepler Radius Distribution and the Kepler-36 Density Dichotomy
• Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets
• The Minimum-Mass Extrasolar Nebula: In-Situ Formation of Close-In Super-Earths
• False positive probabilties for all Kepler Objects of Interest: 1284 newly validated planets and 428 likely false positives
• Planetary evaporation by UV & X-ray radiation: basic hydrodynamics
• Sculpting the Valley in the Radius Distribution of Small Exoplanets as a by-product of Planet Formation: The Core-Powered Mass-Loss Mechanism
• 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
• Kepler-36: A Pair of Planets with Neighboring Orbits and Dissimilar Densities
• Trapping dust particles in the outer regions of protoplanetary disks
• Disks ARound TTauri Stars with Sphere (DARTTS-S) I: Sphere / IRDIS Polarimetric Imaging of 8 prominent TTauri Disks
• The California-Kepler Survey. IV. Metal-rich Stars Host a Greater Diversity of Planets
• Planetary population synthesis coupled with atmospheric escape: a statistical view of evaporation
• Characterization of exoplanets from their formation I: Models of combined planet formation and evolution
• The Compositional Diversity of Extrasolar Terrestrial Planets: I. In-Situ Simulations
• Global simulations of protoplanetary disks with ohmic resistivity and ambipolar diffusion
• Towards Chemical Constraints on Hot Jupiter Migration
• Compositional imprints in density-distance-time: a rocky composition for close-in low-mass exoplanets from the location of the valley of evaporation
• Protoplanetary disc evolution and dispersal: the implications of X-ray photoevaportion
• Formation and Structure of Low Density Exo-Neptunes
• Characterization of exoplanets from their formation II: The planetary mass-radius relationship
• SOPHIE velocimetry of Kepler transit candidates XVII. The physical properties of giant exoplanets within 400 days of period
• A Detailed Model Grid for Solid Planets from 0.1 through 100 Earth Masses
• The coronal X-ray - age relation and its implications for the evaporation of exoplanets
• Model atmospheres of irradiated exoplanets: The influence of stellar parameters, metallicity, and the C/O ratio
• Evolution of Protoplanetary Discs with Magnetically Driven Disc Winds
• Turbulence in the TW Hya Disk
• Ambipolar diffusion in low-mass star formation. I. General comparison with the ideal MHD case
• TESS Discovery of a Transiting Super-Earth in the $\pi$ Mensae System
• Signatures of the Core-Powered Mass-Loss Mechanism in the Exoplanet Population: Dependence on Stellar Properties and Observational Predictions
• A new equation of state for dense hydrogen-helium mixtures
• Molecular abundances and C/O ratios in chemically evolving planet-forming disk midplanes
• Orbital migration of low-mass planets in evolutionary radiative models: Avoiding catastrophic infall
• Global Models of Planet Formation and Evolution
• Testing the theory of grain growth and fragmentation by millimeter observations of protoplanetary disks
• TESS's first planet: a super-Earth transiting the naked-eye star $\pi$ Mensae
• Planetary evolution with atmospheric photoevaporation I. Analytical derivation and numerical study of the evaporation valley and transition from super-Earths to sub-Neptunes
• Composition of Early Planetary Atmospheres I: Connecting Disk Astrochemistry to the Formation of Planetary Atmospheres
• The Role of Magnetic Fields in Protostellar Outflows and Star Formation
• The efficiency of dust trapping in ringed proto-planetary discs
• Constraining planet structure and composition from stellar chemistry: trends in different stellar populations
• Chemistry in an Evolving Protoplanetary Disk: Effects on Terrestrial Planet Composition
• Influence of sub- and super-solar metallicities on the compositions of solid planetary building blocks
• Planetary Populations in the Mass-Period Diagram: A Statistical Treatment of Exoplanet Formation and the Role of Planet Traps
• Formation and structure of the three Neptune-mass planets system around HD69830
• Gas composition of main volatile elements in protoplanetary discs and its implication for planet formation
• On the formation of compact planetary systems via concurrent core accretion and migration
• Low Mg/Si planetary host stars and their Mg-depleted terrestrial planets
• Evolutionary Tracks of Trapped, Accreting Protoplanets: the Origin of the Observed Mass-Period Relation
• Connecting planet formation and astrochemistry: Refractory carbon depletion leading to super-stellar C/O in giant planetary atmospheres
• On the origin of elemental abundances in the terrestrial planets
• Time evolution of snow regions and planet traps in an evolving protoplanetary disk
• C/O vs Mg/Si ratios in solar type stars: The HARPS sample
• The maximum mass of planetary embryos formed in core-accretion models
• Magnetically Induced Disk Winds and Transport in the HL Tau Disk
• On the Formation and Chemical Composition of Super Earths
• From cold to hot irradiated gaseous exoplanets: Toward an observation-based classification scheme
• In hot water: effects of temperature-dependent interiors on the radii of water-rich super-Earths
• Formation of Planetary Populations I: Metallicity & Envelope Opacity Effects
• A pebbles accretion model with chemistry and implications for the solar system
• Trapping planets in an evolving protoplanetary disk: preferred time, locations and planet mass
• Formation of Terrestrial Planets
• Volatiles in protoplanetary disks
• Formation of Planetary Populations II: Effects of Initial Disk Size & Radial Dust Drift
• The effect of the regular solution model in the condensation of protoplanetary dust
• Super-Earths as Failed Cores in Orbital Migration Traps

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• New Perspectives on the Exoplanet Radius Gap from a Mathematica Tool and Visualized Water Equation of State
• Planetary Population Synthesis and the Emergence of Four Classes of Planetary System Architectures
• Combined Effects of Disk Winds and Turbulence-Driven Accretion on Planet Populations
• A Validated Low-to-Intermediate Mass Planetary Interior Structure Model and New Mass-Radius Relations
• The Occurrence-weighted Median Planets Discovered by Transit Surveys Orbiting Solar-type Stars and Their Implications for Planet Formation and Evolution