Lyα flux power spectrum and its covariance

Hu Zhan*, Romeel Davé, Daniel Eisenstein, Neal Katz

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

We analyse the flux power spectrum and its covariance using simulated Lyα 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 Lyα 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 non-linear 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.

Original languageEnglish
Pages (from-to)1145-1154
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Publication statusPublished - 11 Nov 2005

Keywords / Materials (for Non-textual outputs)

  • Cosmology: theory
  • Large-scale structure of Universe
  • Methods: numerical
  • Quasars: absorption lines


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