Numerical simulations of ther 1/4 law

We simulate the evolution of a system of points in a given potential. With a density distribution proportional to r^–n, and a logarithmic potential we obtain a stationary state following ther^1/4 law of de Vaucouleurs. If we follow this simulation to the Galaxy and to M31, we findn=–4 for the Galaxy andn=–3 for M31.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.