The GRAPE board is a special purpose computer designed to solve the gravitational N-body problem directly in hardware. The board installed at the MPA features 8 N-body integrator chips, each of them calculates the gravitational force and potential for up to 131072 particles in parallel. The total computational speed achieved is roughly 5 GFlops. Additionally, GRAPE determines lists of nearest neighbours for the 8 positions under examination. This is extremely useful for smoothed particle hydrodynamics (SPH). The GRAPE board is connected via a VME interface to an ordinary workstation. The communication between GRAPE and front end is conveniently done by calls to a library of C or FORTRAN (strangely enough, people are still using it...) routines.
We study various problems of galaxy formation/evolution and of clusters of galaxies. Among them are:
Galaxy-galaxy mergers and induced starbursts
Semi-analytic merger trees and the formation of elliptical galaxies
Dynamical mixing of collisionless stellar material and dark matter
Mass to light ratio of merger remnants
Structure and dynamics of clusters of galaxies
Magnetic fields in clusters of galaxies
Here is an example of the kind of systems Volker Springel is attempting to simulate. The pictures show the system NGC 4038/4039, a pair of interacting spiral galaxies, also known as the antennae galaxies. The picture on the left shows a wide angle image, the one in the middle a recent ISO observation of the central region. This infrared image shows a region with strong star formation between the nuclei of the merging systems, as may be seen by comparing with the optical image on the right.
Several different codes are used at MPA to address the problems listed above.
Based on GrapeSPH, Volker Springel has developed a new SPH-code in C, which differs in a number of points from GrapeSPH.
Andreas Huss is using GRAPE for simulations of clusters of galaxies. His code combines GRAPE with a particle-mesh (PM) scheme.
Questions or comments? Send email to Volker Springel at firstname.lastname@example.org
Last modified: July 31, 1997