[P-PS07] Planetary Sciences

[PPS07-18] Semi-analytical model for collisional evolution of multiple protoplanet system

*Tadahiro Kimura¹, Haruka Hoshino¹, Eiichiro Kokubo², Masahiro Ikoma² (1.The University of Tokyo, 2.Division of Science, National Astronomical Observatory of Japan)

In the current view of planet formation, multiple planets gather in the vicinity of the central star with relatively narrow orbital spacings after their growth and migration in a protoplanetary disc. Once the disc gas dissipates, these planets experience orbital instability, followed by giant collisions and orbital scatterings, which determine the final planetary masses and orbital architectures. N-body calculations often used to follow this evolution are, however, too computationally expensive to generate many planetary population synthesis models enough for statistical comparison with observational data. To reduce the computational costs, Ida & Lin (2010) developed a semi-analytical model that describes changes in planetary orbital elements associated with giant impacts and orbital scatterings. Although the dynamical evolution process is generally chaotic, the resulting final orbital and mass distribution is known to have some statistical features. The previous study succeeded in reproducing such statistical features, especially in the orbital region near 1 au around solar-mass stars. On the other hand, in the closer-in regions (around 0.1 au), where many exoplanets have been discovered, the collisional evolution is qualitatively different and cannot be fully represented by the previous model. In this study, we develop a new semi-analytical model based on the previous one, which is applicable to close-in orbits around stars of different masses. We validate our model by comparing it with the results of N-body calculations. We find that our model reproduces well the final mass and orbital distributions obtained from N-body calculations in the range of 0.1-1 au around solar-mass stars and around 0.1 au around M dwarfs (0.2 solar masses). By combining this model with other planet-forming elementary processes, a planetary population synthesis model can be developed that takes into account the interaction of multiple planets while keeping computational costs quite low. Such a model is important for future statistical comparisons with exoplanet observations.