Galaxies simulated by the FMM

Two galaxies rotating in the opposite direction collide. The total number of "stars" in the simulation is about 10000 and the shape of each galaxy has been determined by a pre-simulation until quasi steady-state was observed. Since the simulation is only 2-D and since the number of stars is very limited, the result is at best qualitative but serve here as a demonstration of the speed of the FMM. Also, note that no dark matter has been included in the simulation.


  • The fast multipole method employed in the simulations was detailed in S. Engblom: On well-separated sets and fast multipole methods, in Appl. Numer. Math. 61(10):1096--1102, 2011: (doi).

  • What happens if they rotate in the same direction?

    Stefan Engblom
    Last modified: Mon May 5 13:53:56 MEST 2013