2014/06/30 by Linda Blot, L Blot, Pier-Stefano Corasaniti +5 · 55 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics #Cold dark matter #Cosmology #Cosmology and Gravitation Theories #Covariance #Covariance matrix #Dark energy #Dark matter #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gaussian #Matter power spectrum #Physics #Quantum mechanics #Redshift #Spectral density #Statistical physics #Statistics #Universe #astro-ph.CO
paper · pdf · doi:10.1093/mnras/stu2190
published in Monthly Notices of the Royal Astronomical Society 446(2), 1756-1764 (Oxford University Press) · 9 pages, 8 figures, accepted for publication in MNRAS, covariance matrices available upon request to the authors
arxiv created 2014/10/27 · openalex publication_date 2014/11/21 · arxiv updated 2014/11/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The upcoming generation of galaxy surveys will probe the distribution of matter in the Universe with unprecedented accuracy. Measurements of the matter power spectrum at different scales and red shifts will provide stringent constraints on the cosmological parameters. However, on non-linear scales this will require an accurate evaluation of the covariance matrix. Here, we compute the covariance matrix of the three-dimensional matter density power spectrum for the concordance ΛCDM cosmology from an ensemble of N-body simulations of the Dark Energy Universe Simulation – Parallel Universe Runs (DEUS-PUR). This consists of 12 288 realizations of a (656 h−1 Mpc)3 simulation box with 2563 particles. We combine this set with an auxiliary sample of 96 simulations of the same volume with 10243 particles. We find the N-body mass resolution effect to be an important source of systematic errors on the covariance at high redshift and small intermediate scales. We correct for this effect by introducing an empirical statistical method which provide an accurate determination of the covariance matrix over a wide range of scales including the baryon oscillations interval. Contrary to previous studies that used smaller N-body ensembles, we find the power spectrum distribution to significantly deviate from expectations of a Gaussian random density field at k ≳ 0.25 h Mpc−1 and z < 0.5. This suggests that for the finite-volume surveys, an unbiased estimate of the ensemble-averaged band power at these scales and red shifts may require a more careful assessment of non-Gaussian errors than previously considered.