Radial profile of the Iso-NBody simulation at t = 7 Gyr. We show the Fourier amplitude and phase for the stellar (solid ochre) and DM (dashed grey) components. First: amplitude of the 0th Fourier mode (Σ₀), in units of solar mass. We see that, close to the midplane, the surface density of stars and DM is comparable. Second: relative amplitude of the Fourier mode (Σ₂/Σ₀) at all radii. The relative profile of the spirals is similar, with the relative amplitude of the DM spirals being one order of magnitude smaller than the stellar one (notice the auxiliary axis). Third: pattern speed (Ω_s) of the mode m = 2. Fourth: phase lag (Δϕ₂, long-dashed red line) between the DM and stellar components.