1611.04954
The limits of cosmic shear
Kitching, Alsing, Heavens, Jimenez, McEwen, Verde
Discuss the commonly-used approximates for 2pt cosmic shear statistics. Discuss the 4 most prominent assumptions in they statistic: the flat-sky, tomographic, Limber and configuration-space approximations, that the vast majority of cosmic shear results to date have used simultaneously. Of these approximations, find that the flat-sky approximation suppresses power by >1% on scales of l<100 and the standard Limber approximation implementation enhances power by >5% on scales l<100; in doing so, find an l-dependent factor that has been neglected in analyses to date. To investigate the impact of these approximations, reanalyze the CFHTLenS 2D correlation function results. When using all approximations, reproduce the results that measurements of the matter PS amplitude are in tension with measurement from the CMB Planck data: where a conditional value of sigma8=0.789±0.015 is found from CFHTLenS and sigma8=0.830±0.015 from Planck. When the Limber and flat-sky approximations are not used, find a conditional value of sigma8=0.801±0.016 from CFHTLenS, significantly reducing the tension between Planck CMB results and lensing results from CFHTLenS. When including the additional effect of expected photos biases, find sigma8=0839±0.017 which is consistent with Planck. Also discuss the impact on CMB lensing. For Euclid, LSST, and WFIRST and any current or future survey none of these approximations should be used.
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