The limits of cosmic shear
Abstract
In this paper, we discuss the commonly used limiting cases, or approximations, for two-point cosmic-shear statistics. We discuss the most prominent assumptions in this statistic: the flat-sky (small angle limit), the Limber (Bessel-to-delta function limit) and the Hankel transform (large ℓ-mode limit) approximations; that the vast majority of cosmic-shear results to date have used simultaneously. We find that the combined effect of these approximations can suppress power by ≳ 1 per cent on scales of ℓ ≲ 40. A fully non-approximated cosmic-shear study should use a spherical-sky, non-Limber-approximated power spectrum analysis and a transform involving Wigner small-d matrices in place of the Hankel transform. These effects, unaccounted for, would constitute at least 11 per cent of the total budget for systematic effects for a power spectrum analysis of a Euclid-like experiment; but they are unnecessary.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- August 2017
- DOI:
- 10.1093/mnras/stx1039
- arXiv:
- arXiv:1611.04954
- Bibcode:
- 2017MNRAS.469.2737K
- Keywords:
-
- large-scale structure of Universe;
- cosmology: theory;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 15 pages, accepted to MNRAS