Power Spectrum and Intermittency of Lyα Transmitted Flux of QSO HE 2347–4342

We have studied the power spectrum and the intermittent behavior of the fluctuations in the transmitted flux of HE 2347-4342 Lyα absorption in order to investigate if there is any discrepancy between the ΛCDM model with parameters given by the WMAP and observations on small scales. If the non-Gaussianity of the cosmic mass field is assumed to come only from halos with a universal mass profile of the ΛCDM model, the non-Gaussian behavior of mass field would be effectively measured by its intermittency, because intermittency is a basic statistical feature of the cuspy structures. We have shown that the Lyα transmitted flux field of HE 2347-4342 is significantly intermittent on small scales. With the hydrodynamic simulation, we demonstrate that the ΛCDM model is successful in explaining the power spectrum and intermittency of Lyα transmitted flux. Using statistics ranging from second to eighth order, we find no discrepancy between the ΛCDM model and the observed transmitted flux field and no evidence to support the necessity of reducing the power of density perturbations relative to the standard ΛCDM model up to comoving scales as small as about 0.08 h-1 Mpc. Moreover, our simulation samples show that the intermittency exponent of the Lyα transmitted flux field is probably scale-dependent. This result is different from the prediction of a universal mass profile with a constant power index of the central cusp. The scale dependence of the intermittency exponent indicates that the distribution of baryonic gas is decoupled from the underlying dark matter.