The Study of AutoCorrelation Function on Lyman Alpha Forest of QSOs

Abstract

The Lyman Alpha (Lyα) forest is one of the most powerful cosmologi- cal tools for studying large-scale structures of the universe. The flux autocorrelation function for Lyα forest is used to study the clustering of structures. This paper uses the Lyα forest of 49 high-resolution, high signal-to-noise (S/N > 20) QSO spectra ob- served with VLT/UVES. The studied quasars have emission redshifts in the range of (1.89 < zemi < 3.80). The flux autocorrelation function is calculated for each sample, and then, the effect of metal absorption lines in the Lyα forest on the flux autocorre- lation function is investigated. The results of the present study show that the effect of removing metal absorption lines is more visible in the transition to lower redshifts, where there are relatively fewer Lyα absorption lines. Moreover, the change in the flux autocorrelation function at different redshifts is investigated. The results indicate that the flux autocorrelation function at higher redshifts has a larger average value than that at lower redshifts.