摘要：We analyse three public cosmic shear surveys; the Kilo-Degree Survey (KiDS-450), the Dark Energy Survey (DES-SV) and the Canada France Hawaii Telescope Lensing Survey (CFHTLenS). Adopting the “COSEBIs” statistic to cleanly and completely separate the lensingE-modes from the non-lensingB-modes, we detectB-modes in KiDS-450 and CFHTLenS at the level of ∼2.7σ. For DES-SV we detectB-modes at the level of 2.8σin a non-tomographic analysis, increasing to a 5.5σB-mode detection in a tomographic analysis. In order to understand the origin of these detectedB-modes we measure theB-mode signature of a range of different simulated systematics including PSF leakage, random but correlated PSF modelling errors, camera-based additive shear bias and photometric redshift selection bias. We show that any correlation between photometric-noise and the relative orientation of the galaxy to the point-spread-function leads to an ellipticity selection bias in tomographic analyses. This work therefore introduces a new systematic for future lensing surveys to consider. We find that theB-modes in DES-SV appear similar to a superposition of theB-mode signatures from all of the systematics simulated. The KiDS-450 and CFHTLenSB-mode measurements show features that are consistent with a repeating additive shear bias.
关键词：engravitational lensing: weakmethods: data analysismethods: statisticalsurveyscosmology: observations
