From Newton to Einstein - relativistic dynamics in N-body models of galactic nuclei, using special hardware and grid technologiesPresenter: Rainer Spurzem, U. Heidelberg |
Galactic Nuclei harbour supermassive black holes; in the course of cosmological structure formation galaxies merge, and there is the question what happens to their black holes in the process - ejection, stable binaries, or relativistic coalescence? We study the stellar dynamical problem of two black holes (massive bodies) embedded in a dense post-merger central star cluster. As a first approximation gas dynamics is neglected and the system is a large classical N-body problem. The black holes get close to each other and bound via dynamical friction and superelastic three-body scatterings. Our equations of motion in the simulation contain Post-Newtonian relativistic forces up to the PN2.5 level (including gravitational wave emission); for some favourable initial conditions the time to relativistic merger is very short (order Gyr or less) depending on the eccentricity at the time the black hole binary (BBH) becomes bound. This is evidence that a stalling problem does not exist and many BBH's coalesce. Our Post-Newtonian dynamical model allows to follow the BBH merging process till the ultimate coalescence as well as a quantitative prediction of gravitational wave emission for LISA and pulsar timing experiments. The direct collisional N-body model requires massively parallel computers, as it is provided in the European DEISA supercomputer grid as well as special purpose accelerator hardware (GRAPE and new reconfigurable MPRACE). In the German Astrogrid-D project, embedded in the D-Grid initiative, special hardware and our N-body code NBODY6++ are supported as one of the major test cases.