Analysis of the Lyman-alpha Forest in Cosmological Simulations Using Voigt-Profile Decomposition

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We use an automated Voigt-profile fitting procedure to extract statistical properties of the Lyα forest in a numerical simulation of an Ω=1, cold dark matter (CDM) universe. Our analysis method is similar to that used in most observational studies of the forest, and we compare the simulations to recently published results derived from Keck HIRES spectra. With the Voigt-profile decomposition analysis, the simulation reproduces the large number of weak lines (N HI 10¹⁴ cm⁻²) found in the HIRES spectra. At z=3, the b-parameter distribution has a median of 35 and a dispersion of 20, in reasonable agreement with the observed values. The comparison between our new analysis and recent data strengthens earlier claims that the Lyalpha forest arises naturally in hierarchical structure formation as photoionized gas falls into dark matter potential wells.