Year: 2002
Type: article
Abstract: We measure the filling factor, correlation function, and power spectrum of transmitted flux in a large sample of Lyα forest spectra, comprised of 30 Keck HIRES spectra and 23 Keck LRIS spectra. We infer the linear matter power spectrum P ( k ) from the flux power spectrum P F ( k ), using an improved version of the method of Croft et al. that accounts for the influence of redshift-space distortions, nonlinearity, and thermal broadening on the shape of P F ( k ). The evolution of the shape and amplitude of P ( k ) over the redshift range of the sample ( z ≈ 2-4) is consistent with the predictions of gravitational instability, implying that nongravitational fluctuations do not make a large contribution to structure in the Lyα forest. Our fiducial measurement of P ( k ) comes from a subset of the data with 2.3 < z < 2.9, mean absorption redshift ⟨ z ⟩ = 2.72, and total path length Δ z ≈ 25. It has a dimensionless amplitude Δ 2 ( k p ) = 0.74 at wavenumber k p = 0.03 (km s -1 ) -1 and is well described by a power law of index ν = -2.43 ± 0.06 or by a CDM-like power spectrum with shape parameter Γ' = 1.3 × 10 -3 (km s -1 ) -1 at z = 2.72 (all error bars 1 σ). The correspondence to present-day P ( k ) parameters depends on the adopted cosmology. For Ω m = 0.4, Ω Λ = 0.6, the best-fit shape parameter is Γ = 0.16 h Mpc -1 , in good agreement with measurements from the 2dF Galaxy Redshift Survey, and the best-fit normalization is σ 8 = 0.82(Γ/0.15) -0.44 . Matching the observed cluster mass function and our measured Δ 2 ( k p ) in spatially flat cosmological models requires Ω m = 0.38 + 2.2(Γ - 0.15). Matching Δ 2 ( k p ) in COBE -normalized, flat CDM models with no tensor fluctuations requires Ω m = (0.29 ± 0.04) n -2.89 h , and models that satisfy this constraint are also consistent with our measured logarithmic slope. The Lyα forest complements other observational probes of the linear matter power spectrum by constraining a regime of redshift and length scale not accessible by other means, and the consistency of these inferred parameters with independent estimates provides further support for a cosmological model based on inflation, cold dark matter, and vacuum energy.
Source: The Astrophysical Journal
DOI: 10.1086/344099
Institutions: California Institute of Technology, W.M. Keck Observatory, Center for Astrophysics Harvard & Smithsonian, National Aeronautics and Space Administration, Carnegie Mellon University, The Ohio State University, University of California, Santa Cruz, University of California Observatories, University of California San Diego, University of Chicago, Massachusetts Institute of Technology, University of Massachusetts Amherst
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2090436090