Semi analytic approach to understanding the distribution of neutral hydrogen in the Universe: comparison of simulations with observations

Roy Choudhury, T. ; Srianand, R. ; Padmanabhan, T. (2001) Semi analytic approach to understanding the distribution of neutral hydrogen in the Universe: comparison of simulations with observations The Astrophysical Journal, 559 (1). p. 29. ISSN 0004-637X

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Official URL: http://iopscience.iop.org/0004-637X/559/1/29

Related URL: http://dx.doi.org/10.1086/322327

Abstract

Following Bi & Davidsen, we perform one-dimensional semianalytic simulations along the lines of sight to model the intergalactic medium (IGM). Since 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 predictions with different observations. For the currently favored low-density cold dark matter model (Ωm = 0.4, ΩΛ = 0.6, and h = 0.65), we obtain, using statistics obtained from the transmitted flux, constraints on (1) the combination f = (ΩBh2)2/J-12, where ΩB is the baryonic density parameter and J-12 is the total photoionization rate in units of 10-12 s-1, (2) temperature T0 corresponding to the mean density, and (3) the slope ∨ of the effective equation of state of the IGM at a mean redshift z ⋍ 2.5. We find that 0.8 < T0/ < (104 Κ) < 2.5 and 1.3 < ∨ < 2.3, while the constraint obtained on ƒ is 0.0202 < f < 0.0322. A reliable lower bound on J-12 can be used to put a lower bound on ΩBh2, which can be compared with similar constraints obtained from big bang nucleosynthesis (BBN) and cosmic microwave background radiation studies. We find that if J-12 > 1.2, the lower bound on ΩBh2 is in violation of the BBN value.

Item Type:Article
Source:Copyright of this article belongs to University of Chicago Press.
ID Code:55108
Deposited On:18 Aug 2011 07:51
Last Modified:18 May 2016 07:30

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