Non‐Gaussian Features of Transmitted Flux of QSOs' Lyα Absorption: Intermittent Exponent

We calculate the structure function and intermittent exponent of the 1.) Keckdata, which consists of 29 high resolution, high signal to noise ratio (S/N)QSO Ly$\alpha$ absorption spectra, and 2.)the Ly$\alpha$ forest simulationsamples produced via the pseudo hydro scheme for the low density cold darkmatter (LCDM) model and warm dark matter (WDM) model with particle mass$m_W=300, 600, 800$ and 1000 eV. These two measures detect not onlynon-gaussianities, but also the type of non-gaussianty in the the field. Wefind that, 1.) the structure functions of the simulation samples aresignificantly larger than that of Keck data on scales less than about 100h$^{-1}$ kpc, 2.) the intermittent exponent of the simulation samples is morenegative than that of Keck data on all redshifts considered, 3.) theorder-dependence of the structure functions of simulation samples are closer tothe intermittency of hierarchical clustering on all scales, while the Keck dataare closer to a lognormal field on small scales. These differences areindependent of noise and show that the intermittent evolution modeled by thepseudo-hydro simulation is substantially different from observations, eventhough they are in good agreement in terms of second and lower orderstatistics. (Abridged)Comment: 17 pages, 13 figures. Accepted by Ap