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Swiftest: The Next Generation of a Classic N-Body Integration Tool

Presentation #221.05 in the session Planets and Satellites Dynamics (Poster + Lightning Talk)

Published onOct 23, 2023
Swiftest: The Next Generation of a Classic N-Body Integration Tool

In the formation of planets and satellite systems imperfect accretion occurs when a collision results in the fragmentation of one or both of the bodies involved in the collision. Modeling imperfect accretion in an n-body code can be computationally challenging, and it is often either ignored, such that all collisions lead to perfect mergers, or approximated in some way. In order to investigate problems involving imperfect fragmentation and the evolution of collisional fragments, we have developed a new n-body code called Swiftest. Though based on the earlier Swifter code (which itself a Fortran 90 rewrite of the earlier Fortran 77 Swift), the data structures used by Swiftest have been overhauled to improve the performance of integrations in a multi-CPU shared memory parallel environment. This allows Swiftest versions of integrators, such as SyMBA, to simulate many more particles in a given amount of wall time than previous versions, allowing us to simulate planetary accretion with collisional fragmentation with higher fidelity than previous models were capable of. Swiftest contains a number of improvements over earlier generations of the Swift family of n-body codes, including performance improvements in both serial and parallel environments, a set of Python tools to help generate, run, and process simulations, modernized data storage using the NetCDF library, the inclusion of post-Newtonian dynamics in both the WHM and Helio-based symplectic integrators, and more.

We have developed a collisional outcome model for use in Swiftest called Fraggle. When two massive bodies collide in a Swiftest-SyMBA simulation, the collision is evaluated to determine the kind of collisional outcome that is expected. If the collision would lead to imperfect accretion, Fraggle generates a set of new bodies with self-consistent distributions of mass, position, velocity, and rotation. The position and velocity distributions are determined to be consistent with that expected from the three main collisional regimes that Fraggle currently models: disruption, in which the target body is left largely intact and the fragments are ejected from the impact site, supercatastrophic disruption, in which both the target and projectile bodies are disrupted, and disruptive hit-and-run, in which the projectile is fully disrupted but the fragments continue along the projectile’s original trajectory with some dispersion.

Here we demonstrate the capabilities of Swiftest for modeling the formation and evolution of planetary and satellite systems

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