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We use Principal Component Analysis (PCA) to study the gas dynamics innumerical simulations of typical MCs. Our simulations account for thenon-isothermal nature of the gas and include a simplified treatment of thetime-dependent gas chemistry. We model the CO line emission in apost-processing step using a 3D radiative transfer code. We consider meannumber densities n_0 = 30, 100, 300 cm^{-3} that span the range of valuestypical for MCs in the solar neighbourhood and investigate the slope\alpha_{PCA} of the pseudo structure function computed by PCA for severalcomponents: the total density, H2 density, 12CO density, 12CO J = 1 -> 0intensity and 13CO J = 1 -> 0 intensity. We estimate power-law indices\alpha_{PCA} for different chemical species that range from 0.5 to 0.9, in goodagreement with observations, and demonstrate that optical depth effects caninfluence the PCA. We show that when the PCA succeeds, the combination ofchemical inhomogeneity and radiative transfer effects can influence theobserved PCA slopes by as much as ~ +/- 0.1. The method can fail if the COdistribution is very intermittent, e.g. in low-density clouds where CO isconfined to small fragments.

Principal Component Analysis of Molecular Clouds: Can CO reveal the dynamics?