Formation of solar system analogues – I. Looking for initial conditions through a population synthesis analysis

M P Ronco,O M Guilera,G C De Elía

doi:10.1093/mnras/stx1746

Abstract

Population synthesis models of planetary systems developed during the last $\sim$15 years could reproduce several of the observables of the exoplanet population, and also allowed to constrain planetary formation models. We present our planet formation model, which calculates the evolution of a planetary system during the gaseous phase. The code incorporates relevant physical phenomena for the formation of a planetary system, like photoevaporation, planet migration, gas accretion, water delivery in embryos and planetesimals, a detailed study of the orbital evolution of the planetesimal population, and the treatment of the fusion between embryos, considering their atmospheres. The main goal of this work, unlike other works of planetary population synthesis, is to find suitable scenarios and physical parameters of the disc to form solar system analogs. We are specially interested in the final planet distributions, and in the final surface density, eccentricity and inclination profiles for the planetesimal population. These final distributions will be used as initial conditions for N-body simulations, to study the post-oligarchic formation in a second work. We then consider different formation scenarios, with different planetesimal sizes and different type I migration rates. We find that solar system analogs are favored in massive discs, with low type I migration rates, and small planetesimal sizes. Besides, those rocky planets within their habitables zones are dry when discs dissipate. At last, the final configurations of solar system analogs include information about the mass and semimajor-axis of the planets, water contents, and the properties of the planetesimal remnants.

Highlights

For a long time, the study of planetary systems was restricted to our own Solar system
Our model presents a protoplanetary disc, which is characterized by two components: a gaseous component, evolving due to an α-viscosity driven accretion and photoevaporation processes, and a solid component represented by a planetesimal population being subject to accretion and ejection by the embryos, and radial drift due to gas drag
The main goal of this work is to find, through the population synthesis analysis developed with our model of planet formation, sets of appropriate initial conditions to study, in a future work (PII), the post-oligarchic evolution of planetary systems similar to our own with N-body simulations

Summary

Introduction

The study of planetary systems was restricted to our own Solar system This situation had a drastic change since the discovery of the first exoplanet orbiting a sun-like star, 51 Peg b, in 1995 (Mayor & Queloz 1995). Much of these planets form part of about 610 multiple planet systems These systems represent the final stage of a series of complex processes, where a protoplanetary disc evolves into a planetary system, with a few planets and probably, reservoirs of small bodies, like in our Solar system. These discoveries triggered theoretical studies about the formation and evolution of planetary systems. During more than a decade, several models of planet formation have been developed to study the formation of planetary systems and population synthesis with the aim to reproduce the main properties of the observational sample of exoplanets, and to get a better understanding of the main processes of planetary formation (see Benz et al 2014, for a detailed review)

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