N-body simulations of planet formation via pebble accretion I: First Results

Soko Matsumura, Ramon Brasser, Shigeru Ida

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Abstract

Context: Planet formation with pebbles has been proposed to solve a couple of long-standing issues in the classical formation model. Some sophisticated simulations have been done to confirm the efficiency of pebble accretion. However, there has not been any global N-body simulations that compare the outcomes of planet formation via pebble accretion with observed extrasolar planetary systems.

Aims: In this paper, we study the effects of a range of initial parameters of planet formation via pebble accretion, and present the first results of our simulations.

Methods: We incorporate the pebble accretion model by Ida et al. (2016) in the N-body code SyMBA (Duncan et al. 1998), along with the effects of gas accretion, eccentricity and inclination damping and planet migration in the disc.

Results: We confirm that pebble accretion leads to a variety of planetary systems, but have difficulty in reproducing observed properties of exoplanetary systems, such as planetary mass, semimajor axis, and eccentricity distributions. The main reason behind this is a too-efficient type I migration, which sensitively depends on the disc model. However, our simulations also lead to a few interesting predictions. First, we find that formation efficiencies of planets depend on the stellar metallicities, not only for giant planets, but also for Earths (Es) and Super-Earths (SEs). The dependency for Es/SEs is subtle. Although higher metallicity environments lead to faster formation of a larger number of Es/SEs, they also tend to be lost later via dynamical instability. Second, our results indicate that a wide range of bulk densities observed for Es and SEs is a natural consequence of dynamical evolution of planetary systems. Third, the ejection trend of our simulations suggest that one free-floating E/SE may be expected for two smaller-mass planets.
Original languageEnglish
Article numberA67
Number of pages20
JournalAstronomy and Astrophysics
Volume607
Early online date15 Nov 2017
DOIs
Publication statusPublished - 15 Nov 2017

Keywords

  • Planetary systems
  • Planets and satellites: formation
  • Planets and satellites: dynamical evolution and stability
  • Planets and satellites: general

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