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.
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 language | English |
|---|---|
| Article number | A67 |
| Number of pages | 20 |
| Journal | Astronomy & Astrophysics |
| Volume | 607 |
| Early online date | 15 Nov 2017 |
| DOIs | |
| Publication status | Published - 15 Nov 2017 |
Keywords
- Planetary systems
- Planets and satellites: formation
- Planets and satellites: dynamical evolution and stability
- Planets and satellites: general
