Lyman-alpha absorption spectrum of the primordial intergalactic medium

Abstract

The Ly-alpha absorption by four intergalactic medium (IGM) distribution models in the cold dark matter cosmology is simulated, taking the role of the Doppler effect of the peculiar velocity into account. It is found that the medium can produce forestlike Ly-alpha absorption spectra compatible with those observed by fitting statistically the probability distribution function of the line equivalent width and the two-point correlation function. The peculiar velocity shifts the line positions slightly, but does not affect the line profiles when compared to the thermal broadening of atoms. It is considered that some fundamental physical process of the IGM neglected here should follow the same dynamical behavior as in traditional cloud models.