TY - JOUR

T1 - The matter power spectrum at small scales

T2 - An estimate from the Lyman-alpha forest optical depth

AU - Zaroubi, S.

AU - Nusser, A.

AU - Haehnelt, M.

AU - Kim, T.S.

AU - Viel, M.

N1 - Relation: http://www.rug.nl/
date_submitted:2006
Rights: University of Groningen

PY - 2006/6/21

Y1 - 2006/6/21

N2 - We measure the matter power spectrum from 31 Ly alpha spectra spanning the redshift range of 1.6-3.6. The optical depth, tau, for Ly alpha absorption of the intergalactic medium is obtained from the flux using the inversion method of Nusser & Haehnelt. The optical depth is converted to density by using a simple power-law relation, tau proportional to (1 + delta)(alpha). The non-linear 1D power spectrum of the gas density is then inferred with a method that makes simultaneous use of the one- and two-point statistics of the flux and compared against theoretical models with a likelihood analysis. A cold dark matter model with standard cosmological parameters fits the data well. The power-spectrum amplitude is measured to be (assuming a flat Universe), sigma(8) = (0.92 +/- 0.09) x (Omega(m)/0.3)(-0.3), with alpha varying in the range of 1.56-1.8 with redshift. Enforcing the same cosmological parameters in all four redshift bins, the likelihood analysis suggests some evolution in the temperature-density relation and the thermal smoothing length of the gas. The inferred evolution is consistent with that expected if reionization of He-II occurred at z similar to 3.2. A joint analysis with the Wilkinson Microwave Anisotropy Probe results together with a prior on the Hubble constant as suggested by the Hubble Space Telescope key project data, yields values of Omega(m) and sigma(8) that are consistent with the cosmological concordance model. We also perform a further inversion to obtain the linear 3D power spectrum of the matter density fluctuations.

AB - We measure the matter power spectrum from 31 Ly alpha spectra spanning the redshift range of 1.6-3.6. The optical depth, tau, for Ly alpha absorption of the intergalactic medium is obtained from the flux using the inversion method of Nusser & Haehnelt. The optical depth is converted to density by using a simple power-law relation, tau proportional to (1 + delta)(alpha). The non-linear 1D power spectrum of the gas density is then inferred with a method that makes simultaneous use of the one- and two-point statistics of the flux and compared against theoretical models with a likelihood analysis. A cold dark matter model with standard cosmological parameters fits the data well. The power-spectrum amplitude is measured to be (assuming a flat Universe), sigma(8) = (0.92 +/- 0.09) x (Omega(m)/0.3)(-0.3), with alpha varying in the range of 1.56-1.8 with redshift. Enforcing the same cosmological parameters in all four redshift bins, the likelihood analysis suggests some evolution in the temperature-density relation and the thermal smoothing length of the gas. The inferred evolution is consistent with that expected if reionization of He-II occurred at z similar to 3.2. A joint analysis with the Wilkinson Microwave Anisotropy Probe results together with a prior on the Hubble constant as suggested by the Hubble Space Telescope key project data, yields values of Omega(m) and sigma(8) that are consistent with the cosmological concordance model. We also perform a further inversion to obtain the linear 3D power spectrum of the matter density fluctuations.

KW - hydrodynamics

KW - intergalactic medium

KW - quasars : absorption lines

KW - cosmology : theory

KW - large-scale structure of Universe

KW - COLD DARK-MATTER

KW - PROBE WMAP OBSERVATIONS

KW - QSO ABSORPTION-SPECTRA

KW - QUASI-STELLAR OBJECTS

KW - INTERGALACTIC MEDIUM

KW - HYDRODYNAMICAL SIMULATIONS

KW - COSMOLOGICAL PARAMETERS

KW - BACKGROUND ANISOTROPIES

KW - MASS FLUCTUATIONS

KW - HUBBLE CONSTANT

U2 - 10.1111/j.1365-2966.2006.10333.x

DO - 10.1111/j.1365-2966.2006.10333.x

M3 - Article

SN - 0035-8711

VL - 369

SP - 734

EP - 750

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 2

ER -