Detecting the non-Gaussian Spectrum of QSO's Ly$α$ Absorption Line Distribution

Abstract

We present an analysis of the non-Gaussianity in the distribution of Ly$α$ forest lines in the QSO absorption spectra. Statistical tests performed on this data indicate that there may be large scale structure even though the power spectrum of the Ly$α$ line distribution on large scales is found to be flat. It is apparent that higher (than two) order statistics are crucial in quantifying the clustering behavior of Ly$α$ clouds. Using the discrete wavelet on three independent data sets of Ly$α$ forests, we find that the distribution of Ly$α$ forests does show non-Gaussian behavior on scales from 5 to 10 h$^{-1}$ Mpc with confidence level larger than 95%. Two data sets available on large scales are found to be non-Gaussian on even larger scales. These techniques are effective in discriminating among models of the Ly$α$ forest formation, which are degenerate at second and lower order statistics (abridged).