SUPERBOX - an efficient code for collisionless galactic dynamics

We present SUPERBOX, a particle-mesh code with high resolution sub-grids and an NGP (nearest grid point) force-calculation scheme based on the second derivatives of the potential. SUPERBOX implements a fast low-storage FFT-algorithm, giving the possibility to work with millions of particles on desk-top computers. Test calculations show energy and angular momentum conservation to one part in 10(5) per crossing-time. The effects of grid and numerical relaxation remain negligible, even when these calculations cover a Hubble-time of evolution. As the sub-grids follow the trajectories of individual galaxies, the code allows a highly resolved treatment of interactions in clusters of galaxies, such as high-velocity encounters between elliptical galaxies and the tidal disruption of dwarf galaxies. Excellent agreement is obtained in a comparison with a direct-summation N-body code running on special-purpose GRAPE 3 hardware. The orbital decay of satellite galaxies due to dynamical friction obtained with SUPERBOX agrees with Chandrasekhar's treatment when the Coulomb logarithm ln Lambda approximate to 1.5. (C) 2000 Elsevier Science B. V. All rights reserved.