Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2009-06-12
Astrophys.J.701:945-954,2009
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
11 pages, 11 figures. Accepted for publication in the Astrophysical Journal. Corrected typo in the equation of survey window f
Scientific paper
10.1088/0004-637X/701/2/945
We study the lensing convergence power spectrum and its covariance for a standard LCDM cosmology. We run 400 cosmological N-body simulations and use the outputs to perform a total of 1000 independent ray-tracing simulations. We compare the simulation results with analytic model predictions. The semi-analytic model based on Smith et al.(2003) fitting formula underestimates the convergence power by ~30% at arc-minute angular scales. For the convergence power spectrum covariance, the halo model reproduces the simulation results remarkably well over a wide range of angular scales and source redshifts. The dominant contribution at small angular scales comes from the sample variance due to the number fluctuations of halos in a finite survey volume. The signal-to-noise ratio for the convergence power spectrum is degraded by the non-Gaussian covariances by up to a factor 5 for a weak lensing survey to z_s ~1. The probability distribution of the convergence power spectrum estimators, among the realizations, is well approximated by a chi-square distribution with broadened variance given by the non-Gaussian covariance, but has a larger positive tail. The skewness and kurtosis have non-negligible values especially for a shallow survey. We argue that a prior knowledge on the full distribution may be needed to obtain an unbiased estimate on the ensemble averaged band power at each angular scale from a finite volume survey.
Hamana Takashi
Matsubara Takahiko
Sato Masanori
Sugiyama Naoshi
Takada Masahiro
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