Linking planetary embryo formation to planetesimal formation

Oliver Voelkel,Hubert Klahr,Katherine Kretke,Rogerio Deienno

doi:10.1051/0004-6361/202039245

Oliver Voelkel, Hubert Klahr + Show 2 more

Open Access

https://doi.org/10.1051/0004-6361/202039245

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Abstract

Context.The accretion of pebbles onto planetary cores has been widely studied in recent years and is found to be a highly effective mechanism for planetary growth. While most studies assume planetary cores as an initial condition in their simulation, the question of the manner, location, and time at which these cores form is often neglected.Aims.We study the effect of pebble accretion during the formation phase and subsequent evolution of planetary embryos in the early stages of circumstellar disk evolution. In doing so, we aim to quantify the timescales and local dependence of planetary embryo formation based on the solid evolution of the disk.Methods.We connected a one-dimensional two-population model for solid evolution and pebble-flux-regulated planetesimal formation to theN-body code LIPAD. We focused on the growth of planetesimals with an initial size of 100 km in diameter by planetesimal collisions and pebble accretion for the first one million years of a viscously evolving disk. We compared 18 differentN-body simulations in which we varied the total planetesimal mass after one million years, the surface density profile of the planetesimal disk, the radial pebble flux, and the possibility of pebble accretion.Results.Pebble accretion leads to the formation of fewer but substantially more massive embryos. The area of possible embryo formation is weakly affected by the accretion of pebbles, and the innermost embryos tend to form slightly earlier than in simulations in which pebble accretion is neglected.Conclusions.Pebble accretion strongly enhances the formation of super-Earths in the terrestrial planet region, but it does not enhance the formation of embryos at larger distances.

Highlights

The accretion of solids and eventually gas (Pollack et al 1996) onto planetary cores is widely used as the standard scenario for planet formation
Most studies in the field of planet formation begin with an initial planetary core that grows by either planetesimal (Ida & Lin 2004; Mordasini et al 2012; Emsenhuber et al 2020a,b; Voelkel et al 2020) or pebble accretion (Bitsch et al 2015, Ndugu et al 2017, Lambrechts & Johansen 2012)
We here present an expansion of our companion paper (Voelkel et al 2021), in which we investigated the formation of planetary embryos from a dynamically evolving planetesimal disk and derived a onedimensional parameterized analytic model for planetary embryo formation

Summary

Introduction

The accretion of solids and eventually gas (Pollack et al 1996) onto planetary cores is widely used as the standard scenario for planet formation. Recent work included the consistent formation (Lenz et al 2019) and accretion of planetesimals onto planetary embryos into a global model of planet formation (Voelkel et al 2020). A fully consistent global model for planet formation would have to form planetary embryos based on the previous evolution of the system. Studies that form planetary embryos from planetesimals usually neglect the formation of the planetesimals by assuming an initial distribution in the disk (Levison et al 2015; Walsh & Levison 2015; Carter et al 2015; Clement et al 2020). The effect of pebble accretion (Ormel & Klahr 2010; Klahr & Bodenheimer 2006) on the formation of planetary embryo formation is added to the same framework in this study

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