Model. N equal-mass particles stand for gas clouds of a protogalaxy (total M = 1011 M☉, initial radius 30 kpc, G = 1; time unit √(R³/GM) = 0.245 Gyr, velocity unit 119.7 km/s). Pair forces are Plummer-softened, ai = Σ G m (rj−ri)/(|r|²+ε²)3/2, advanced with a symplectic kick-drift-kick leapfrog.
Dark halo. A static Plummer sphere, Φ(r) = −G Mh/√(r²+a²), a = 1.5 R. It does not respond to the gas (a simplification).
Cooling. A friction term damps radial and vertical motion down to a small floor, so the cloud settles onto a rotating disc. It is a toy for dissipation, not a cooling-function model.
Rotation curve. Circular speed from the spherical enclosed mass (particles plus halo), an approximation for a thin disc. Measured speeds are binned in cylindrical radius.
Not modelled: star formation, gas pressure, feedback, a live halo, cosmological infall. With a few hundred to a couple of thousand particles, relaxation noise exceeds that of real galaxies. The Blender model (table, rings, halo shell, satellite texture, sky) is illustration only.