Lyα flux power spectrum and its covariance

Hu Zhan, Romeel Davé, Daniel Eisenstein, Neal Katz

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


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 (US)
Pages (from-to)1145-1154
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Nov 11 2005


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

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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