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

We have studied the power spectrum and the intermittent behavior of thefluctuations in the transmitted flux of HE2347-4342 ${\rm Ly}{\alpha}$absorption in order to investigate if there is any discrepancy between the LCDMmodel with parameters given by the WMAP and observations on small scales. Ifthe non-Gaussianity of cosmic mass field is assumed to come only from haloswith an universal mass profile of the LCDM model, the non-Gaussian behavior ofmass field would be effectively measured by its intermittency, becauseintermittency is a basic statistical feature of the cuspy structures. We haveshown that the Ly$\alpha$ transmitted flux field of HE2347-4342 issignificantly intermittent on small scales. With the hydrodynamic simulation,we demonstrate that the LCDM model is successful in explaining the powerspectrum and intermittency of ${\rm Ly}{\alpha}$ transmitted flux. Usingstatistics ranging from the second to eighth order, we find no discrepancybetween the LCDM model and the observed transmitted flux field, and no evidenceto support the necessity of reducing the power of density perturbationsrelative to the standard LCDM model up to comoving scales as small as about$0.08 {\rm h}^{-1} {\rm Mpc}$. Moreover, our simulation samples show that theintermittent exponent of the Ly$\alpha$ transmitted flux field is probablyscale-dependent. This result is different from the prediction of universal massprofile with a constant index of the central cusp. The scale-dependence of theintermittent exponent indicates that the distribution of baryonic gas isdecoupled from the underlying dark matter.Comment: 27 pages (incl. 8 figures). Accepted for publication in Ap