N-body Simulations in Galactic Potentials

Sammanfattning: What effect does a collision between two clusters have on their dissolving time? In order to answer this question, a new type of N-body simulation using a double integration of a cluster was built. Instead of introducing a perturbation representing the gravitational force of the Milky Way into a local simulation of the cluster, the cluster orbit was integrated in the potential of the Milky Way, and in each of these integration steps the local motion of the stars inside the cluster were integrated, using an N-body calculation. The goal of this new type of integrator was to create a more versatile and intuitive simulation, where no perturbation calculation was needed before initiating a cluster. The simulation as a whole was tested using different resolutions and relative tolerances, and both the N-body calculation and potential integration were tested separately as well as in conjunction. As a test subject, the Hyades open cluster was investigated in this project. The number of stars within the tidal radius of the cluster as a function of time was calculated, and the effect of cluster collisions on the decay rate was investigated. The results are also highly indicative of that the star HD31236 is not an actual member of the Hyades, though this needs further testing, taking the formal errors of the initial conditions into account.