Ly&alpha forest absorption line parameter distributions

line parameters

Comparison between the cumulative distributions of the neutral hydrogen column densities (left panel) and widths (Doppler parameters; right panel) measured in QSO Q1937-1009 and the predictions of a cosmological constant model (long dashed). The predictions for the same model are also shown with the absorption lines convolved with a 12 km/s gaussian, comparable to the amount of extra thermal energy that may be deposited by including radiative transfer effects with late HeII reionisation. The broadened absorption lines much improve the agreement in velocity width distributions and brings into near perfect agreement the distributions in neutral hydrogen column densities. Ultimately reionisation must be incorporated into the numerical simulations to provide refined predictions for the absorption line parameters and resolve the discrepancy shown in Figure 3. (From Meiksin, Bryan & Machacek 2001.)

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