A tree code for planetesimal dynamics: Comparison with a hybrid direct code

We present a tree code for simulations of collisional systems dominated by a central mass. We describe the implementation of the code and the results of some test runs with which the performance of the code was tested. A comparison between the behaviour of the tree code and a direct hybrid integrator is also presented. The main result is that tree codes can be useful in numerical simulations of planetary accretion, especially during intermediate stages, where possible runaway accretion and dynamical friction lead to a population with a few large bodies in low-eccentricity and low-inclination orbits embedded in a large swarm of small planetesimals in rather excited orbits. Some strategies to improve the performance of the code are also discussed.Facultad de Ciencias Astronómicas y Geofísica

A tree code for planetesimal dynamics: Comparison with a hybrid direct code

We present a tree code for simulations of collisional systems dominated by a central mass. We describe the implementation of the code and the results of some test runs with which the performance of the code was tested. A comparison between the behaviour of the tree code and a direct hybrid integrator is also presented. The main result is that tree codes can be useful in numerical simulations of planetary accretion, especially during intermediate stages, where possible runaway accretion and dynamical friction lead to a population with a few large bodies in low-eccentricity and low-inclination orbits embedded in a large swarm of small planetesimals in rather excited orbits. Some strategies to improve the performance of the code are also discussed.Facultad de Ciencias Astronómicas y Geofísica

Parallelized tree-code for clusters of personal computers

We present a tree-code for integrating the equations of the motion of collisionless systems, which has been fully parallelized and adapted to run in several PC-based processors simultaneously, using the well-known PVM message passing library software. SPH algorithms, not yet included, may be easily incorporated to the code. The code is written in ANSI C; it can be freely downloaded from a public ftp site. Simulations of collisions of galaxies are presented, with which the performance of the code is tested.Facultad de Ciencias Astronómicas y Geofísica

On the number of particles in N-body simulations of planet disk interaction

In this paper we present a new mixed-variables symplectic tree code for planetesimal dynamics, which allows to use a very large number of particles in numerical simulations of planet disk interaction. Furthermore, we discuss how a wrong election of the number of particles to model a planetesimal disk, in order to carry out realistic numerical simulations, can cause spurious result. If the particle number is not enough, the close encounter between the planet and unrealistic massive particles will introduce a stochastic component of planet migration. This has an impact on the migration rate and it can even change its sign. Finally, we describe how to determine the minimum number of disk particles that should be used in numerical simulations, in order to have a correct description of the interaction, especially when the dynamical friction on the planet is the relevant mechanism of migration.Grupo de Ciencias Planetarias (GCP