A break in planet occurrence near the pebble isolation mass should be observable by the Roman microlensing survey

Abstract

Microlensing detections are uniquely well-suited to probing the population of planets outside the water iceline, down to planetary masses comparable to the Earth. Here, we perform 1D pebble-accretion population synthesis simulations to explore a sample of iceline planets around stars with masses and metallicities similar to the target population of the Galactic Bulge Time-domain microlensing survey of the Nancy Grace Roman Space Telescope. We find that the planet distribution in the microlensing sensitivity space deviates from a log-uniform distribution in mass and orbital radius. When planetary core growth comes to a halt as planets reach the pebble isolation mass, $M_{\mathrm{iso}}$, the combined effects of planetary migration and runaway gas accretion create an occurrence break. Our simulations highlight that, between 1 and 50 AU, the fraction of stars hosting isolation-mass planets (1 to 5 $M_{\mathrm{iso}}$) is lower by a factor 20 compared to less massive planets (0.2 to 1 $M_{\mathrm{iso}}$). If this break in planetary occurrence rates around the pebble isolation mass is detected in future lensing surveys, it would further validate the core accretion paradigm for giant planet formation.

arXiv comment9 pages, 7 figures, accepted for publication in A&A

References in corpus (54)

• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• Towards a Deterministic Model of Planetary Formation I: a Desert in the Mass and Semi Major Axis Distributions of Extra Solar Planets
• Rapid growth of gas-giant cores by pebble accretion
• Coagulation, fragmentation and radial motion of solid particles in protoplanetary disks
• The effect of gas drag on the growth of protoplanets -- Analytical expressions for the accretion of small bodies in laminar disks
• Separating gas-giant and ice-giant planets by halting pebble accretion
• A torque formula for non-isothermal Type I planetary migration - I. Unsaturated horseshoe drag
• Dust and Gas in the disc of HL Tauri: Surface density, dust settling, and dust-to-gas ratio
• X-Shooter spectroscopy of young stellar objects: IV -- Accretion in low-mass stars and sub-stellar objects in Lupus
• The Magnetic Fields of Classical T Tauri Stars
• The Luminosity and Mass Functions of Low-Mass Stars in the Galactic Disk: II. The Field
• Frequency of Solar-Like Systems and of Ice and Gas Giants Beyond the Snow Line from High-Magnification Microlensing Events in 2005-2008
• The initial mass function : from Salpeter 1955 to 2005
• A stellar-mass-dependent drop in planet occurrence rates
• Pebble isolation mass --- scaling law and implications for the formation of super-Earths and gas giants
• Statistical properties of exoplanets II. Metallicity, orbital parameters, and space velocities
• Spectroscopic metallicities for planet-host stars: extending the samples
• Predictions of the WFIRST Microlensing Survey I: Bound Planet Detection Rates
• The Exoplanet Mass-Ratio Function from the MOA-II Survey: Discovery of a Break and Likely Peak at a Neptune Mass
• Gas Flow Across Gaps in Protoplanetary Disks
• About 30% of Sun-like Stars Have Kepler-like Planetary Systems: A Study of their Intrinsic Architecture
• Formation of planetary systems by pebble accretion and migration: How the radial pebble flux determines a terrestrial-planet or super-Earth growth mode
• Radial migration of gap-opening planets in protoplanetary disks. I. The case of a single planet
• An Increase in the Mass of Planetary Systems around Lower-Mass Stars
• The New Generation Planetary Population Synthesis (NGPPS). IV. Planetary systems around low-mass stars
• Evidence for a correlation between mass accretion rates onto young stars and the mass of their protoplanetary disks
• Dust masses of young disks: constraining the initial solid reservoir for planet formation
• The New Generation Planetary Population Synthesis (NGPPS). I. Bern global model of planet formation and evolution, model tests, and emerging planetary systems
• X-Shooter study of accretion in Chamaeleon I: II. A steeper increase of accretion with stellar mass for very low mass stars?
• The radial dependence of pebble accretion rates: A source of diversity in planetary systems I. Analytical formulation
• The CARMENES search for exoplanets around M dwarfs -- Planet occurrence rates from a subsample of 71 stars
• Mapping accretion and its variability in the young open cluster NGC 2264: a study based on u-band photometry
• Final Masses of Giant Planets II: Jupiter Formation in a Gas-Depleted Disk
• Super-Earth masses sculpted by pebble isolation around stars of different masses
• How planetary growth outperforms migration
• HST measures of Mass Accretion Rates in the Orion Nebula Cluster
• Occurrence Rates of Planets Orbiting M Stars: Applying ABC to Kepler DR25, Gaia DR2, and 2MASS Data
• A stellar mass dependence of structured disks: a possible link with exoplanet demographics
• Microlensing Results Challenge the Core Accretion Runaway Growth Scenario for Gas Giants
• Dynamical rearrangement of super-Earths during disk dispersal I. Outline of the magnetospheric rebound model
• Pebble-driven Planet Formation around Very Low-mass Stars and Brown Dwarfs
• Why do M dwarfs have more transiting planets?
• X-shooter spectroscopy of young stars with disks. The TW Hydrae association as a probe of the final stages of disk accretion
• Microlensing events indicate that super-Earth exoplanets are common in Jupiter-like orbits
• Small Planets Around Cool Dwarfs: Enhanced Formation Efficiency of Super-Earths around M dwarfs
• Characterizing Lenses and Lensed Stars of High-Magnification Single-lens Gravitational Microlensing Events With Lenses Passing Over Source Stars
• Mass measurement of a single unseen star and planetary detection efficiency for OGLE 2007-BLG-050
• Disc population synthesis: Decrease in the solid mass reservoir through pebble drift
• Migration and Growth of Protoplanetary Embryos II: Emergence of Proto-Gas-Giants Cores versus Super Earths' Progenitor
• Super-Earth formation in systems with cold giants
• The New Generation Planetary Population Synthesis (NGPPS). VII. Statistical comparison with the HARPS/Coralie survey
• The New Generation Planetary Population Synthesis (NGPPS) VIII. Impact of host star metallicity on planet occurrence rates, orbital periods, eccentricities, and radius valley morphology
• New migration patterns in high planet-star mass ratio systems in disks with low viscosity
• How stellar mass and disc size shape the formation and migration of super-Earths