Lyman Alpha Flux Power Spectrum and Its Covariance

Abstract

We analyze the flux power spectrum and its covariance using simulated Lyman alpha forests. We find that pseudo-hydro techniques are good approximations of hydrodynamical simulations at high redshift. However, the pseudo-hydro techniques fail at low redshift because they are insufficient for characterizing some components of the low-redshift intergalactic medium, notably the warm-hot intergalactic medium. Hence, to use the low-redshift Lyman alpha flux power spectrum to constrain cosmology, one would need realistic hydrodynamical simulations. By comparing one-dimensional mass statistics with flux statistics, we show that the nonlinear transform between density and flux quenches the fluctuations so that the flux power spectrum is much less sensitive to cosmological parameters than the one-dimensional mass power spectrum. The covariance of the flux power spectrum is nearly Gaussian. As such, the uncertainties of the underlying mass power spectrum could still be large, even though the flux power spectrum can be precisely determined from a small number of lines of sight.

arXiv comment10 pages, 15 figures, accepted for publication in MNRAS

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Cited by in corpus (8)

• The Physics of the Intergalactic Medium
• On measuring the covariance matrix of the nonlinear power spectrum from simulations
• The intergalactic medium over the last 10 billion years I: Lyman alpha absorption and physical conditions
• Intergalactic Lyman continuum photon budget in the past 5 billion years
• Numerical Simulations of the Lyman-alpha forest - A comparison of Gadget-2 and Enzo
• Reconstruction of the neutrino mass as a function of redshift
• Testing the accuracy of the Hydro-PM approximation in numerical simulations of the Lyman-alpha forest
• Efficient adiabatic hydrodynamical simulations of the high-redshift intergalactic medium