Metallicity effect and planet mass function in pebble-based planet formation models

Abstract

One of the main scenarios of planet formation is the core accretion model where a massive core forms first and then accretes a gaseous envelope. This core forms by accreting solids, either planetesimals, or pebbles. A key constraint in this model is that the accretion of gas must proceed before the dissipation of the gas disc. Classical planetesimal accretion scenario predicts that the time needed to form a giant planets core is much longer than the time needed to dissipate the disc. This difficulty led to the development of another accretion scenario, in which cores grow by accretion of pebbles, which are much smaller and thus more easily accreted, leading to a more rapid formation. The aim of this paper is to compare our updated pebble-based planet formation model with observations, in particular the well studied metallicity effect. We adopt the Bitsch et al. 2015a disc model and the Bitsch et al. 2015b pebble model and use a population synthesis approach to compare the formed planets with observations. We find that keeping the same parameters as in Bitsch et al. 2015b leads to no planet growth due to a computation mistake in the pebble flux (Bitsch et al. 2017). Indeed a large fraction of the heavy elements should be put into pebbles (Zpeb/Ztot = 0.9) in order to form massive planets using this approach. The resulting mass functions show a huge amount of giants and a lack of Neptune mass planets, which are abundant according to observations. To overcome this issue we include the computation of the internal structure for the planetary atmosphere to our model. This leads to the formation of Neptune mass planets but no observable giants. Reducing the opacity of the planetary envelope finally matches observations better. We conclude that modeling the internal structure for the planetary atmosphere is necessary to reproduce observations.

13 pages, 22 figures

References in corpus (13)

• Pebble isolation mass --- scaling law and implications for the formation of super-Earths and gas giants
• The structure of protoplanetary discs around evolving young stars
• Radial migration of gap-opening planets in protoplanetary disks. I. The case of a single planet
• Hydrodynamics of Embedded Planets' First Atmospheres. II. A Rapid Recycling of Atmospheric Gas
• Reduced gas accretion on super-Earths and ice giants
• Planet formation with envelope enrichment: new insights on planetary diversity
• Formation of dust-rich planetesimals from sublimated pebbles inside of the snow line
• How much does turbulence change the pebble isolation mass for planet formation?
• Planet population synthesis driven by pebble accretion in cluster environments
• From planetesimals to planets: volatile molecules
• Grain opacity and the bulk composition of extrasolar planets. I. Results from scaling the ISM opacity
• Toward a new paradigm for Type II migration
• Slowing Down Type II Migration of Gas Giants to Match Observational Data

Cited by in corpus (23)

• The New Generation Planetary Population Synthesis (NGPPS). IV. Planetary systems around low-mass stars
• Formation of planetary systems by pebble accretion and migration: Growth of gas giants
• How drifting and evaporating pebbles shape giant planets I: Heavy element content and atmospheric C/O
• How planetary growth outperforms migration
• How drifting and evaporating pebbles shape giant planets II: Volatiles and refractories in atmospheres
• Heavy metal rules. I. Exoplanet incidence and metallicity
• Pebbles versus Planetesimals: The case of Trappist-1
• How dust fragmentation may be beneficial to planetary growth by pebble accretion
• RV-detected planets around M dwarfs: Challenges for core accretion models
• Pebbles versus planetesimals: the outcomes of population synthesis models
• The impact of pebble flux regulated planetesimal formation on giant planet formation
• The New Generation Planetary Population Synthesis (NGPPS). VI. Introducing KOBE: Kepler Observes Bern Exoplanets. Theoretical perspectives on the architecture of planetary systems: Peas in a pod
• Setting the Stage: Planet formation and Volatile Delivery
• Are the observed gaps in protoplanetary discs caused by growing planets?
• How to make giant planets via pebble accretion
• Probing the impact of varied migration and gas accretion rates for the formation of giant planets in the pebble accretion scenario
• Using Deep Neural Networks to compute the mass of forming planets
• The interplay between pebble and planetesimal accretion in population synthesis models and its role in giant planet formation
• Planetary core formation via multi-species pebble accretion
• How Flow Isolation May Set the Mass Scale for Super-Earth Planets
• The Pedagogical Representation of Mass Functions with LEGO and their Origin
• The PAIRS project: a global formation model for planets in binaries. II. Gravitational perturbation effects from secondary stars
• A large sub-Neptune transiting the thick-disk M4V TOI-2406