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Orbits of Galaxies

  With the information from the two previous chapters, we are now ready to test the AVP on real systems of galaxies. A complete algorithm for the determination of stationary values for such a system will then be needed. A description of such a program, AVP, in which any of the optimization methods from Chapter 4 can be inserted, will be given in Section 5.1, where it also will be applied to a system consisting of eight galaxies in the LG and the LN. Next, in Section 5.2, the N-body code used to test the validity of the action solutions, NBODY1, will be presented. NBODY1 was kindly provided by the author of the code, Dr. Sverre Aarseth. The different optimizing methods from Section 4.3 will be tested on the eight particle system in Section 5.3, while in Section 5.4, the test will be extended to a larger, more realistic, system of particles, consisting of 22 mass tracers. These two systems of mass tracers will serve as two distinctly different testing grounds, which, hopefully, will enable us to determine which optimizing method work best for what type of system. Also given in Section 5.4 is a physical discussion of the solutions of the larger system, trying to fit the model with observations. All the calculations in this chapter were performed in double precision on a Digital Personal Workstation with a 500 MHz 21264 Alpha processor (EV6).

Trond Hjorteland
Mon Jul 5 02:59:28 MET DST 1999