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Following Bi & Davidsen (1997), we perform 1D semi analytic simulations along the lines of sight to model the intergalactic medium (IGM). As this procedure is computationally efficient in probing the parameter space -- and reasonably accurate -- we use it to recover the values of various parameters related to the IGM (for a fixed background cosmology) by comparing the model with various observations. For LCDM model with \ₘ=0. 4, \\=0. 6 and h=0. 65, we obtain constraints on the baryonic density parameter (\B), temperature corresponding to the mean density (T₀) and the slope of the equation of state of the IGM (\) at a mean redshift z \ 2. 5, using statistics obtained from the transmitted flux. Previous attempts in recovering T₀ and \ made use of the lower cutoff of the distribution of line widths (i. e. , b parameter), which can introduce several biases and systematic errors in the inferred values of \ and T₀. Our method is comparatively free of such errors. We find that 0. 8< (T₀/10⁴ K) <2. 5 and 1. 3<\<2. 3. The constraint obtained on the combination f= (\B h²) ²/J-₁₂ is 0. 020²<f<0. 032², where J-₁₂ is the total photoionisation rate in units of 10^-12s^-1. We note that a reliable estimate of J-₁₂ can be used to constrain \B h², and the resulting bound can be compared with similar constraints obtained from Big Bang Nucleosynthesis and CMBR studies.
Choudhury et al. (Thu,) studied this question.