Power spectra from synthetic observations of the large-scale ISM simulation. The power P is calculated for the true column density, the 250 μm dust surface brightness, and for three versions of ¹²CO line-area maps. The ¹²CO emission corresponds either to a constant abundance of χ₀ = 10⁻⁴ and LTE conditions or to the Eq. (4) abundances with LTE or non-LTE calculations. The grey lines correspond to least-squares fits and extend over the range of the fitted spatial frequencies.