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Weak-lensing statistics from the Coyote Universe


  • Tim Eifler

    Corresponding author
    1. Center for Cosmology and Astro-Particle Physics, The Ohio State University, 191 W. Woodruff Avenue, Columbus, OH 43210, USA
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Analysing future weak-lensing data sets from KIDS, Dark Energy Survey (DES), LSST, Euclid and WFIRST requires precise predictions for the weak-lensing measures. In this paper, we present a weak-lensing prediction code based on the Coyote Universe emulator. The Coyote Universe emulator predicts the (non-linear) power spectrum of density fluctuations (Pδ) to high accuracy for k∈[0.002; 3.4] h Mpc−1 within the redshift interval z∈[0; 1]; outside this regime, we extend Pδ using a modified halofit code.

This pipeline is used to calculate various second-order cosmic shear statistics, e.g., shear power spectrum, shear–shear correlation function, ring statistics and Complete Orthogonal Set of EB-mode Integrals (COSEBIs), and we examine how the upper limit in k (and z), to which Pδ is known, impacts on these statistics. For example, we find that kmax∼ 8 h Mpc−1 causes a bias in the shear power spectrum at ℓ∼ 4000 that is comparable to the statistical errors (intrinsic shape noise and cosmic variance) of a DES-like survey, whereas for LSST-like errors kmax∼ 15 h Mpc−1 is needed to limit the bias at ℓ∼ 4000.

For the most recently developed second-order shear statistics, the COSEBIs, we find that nine modes can be calculated accurately knowing Pδ to kmax= 10 h Mpc−1. The COSEBIs allow for an EB-mode decomposition using a shear–shear correlation function measured over a finite range, thereby avoiding any EB-mode mixing due to finite survey size. We perform a detailed study in a five-dimensional parameter space in order to examine whether all cosmological information is captured by these nine modes with the result that already 7–8 modes are sufficient.