KiDS-1000 cosmic shear reanalysis using MetaCalibration

Abstract

A number of cosmic shear studies have reported results that are in mild tension with Planck cosmic microwave background measurements. To explore if this can be caused by biases in shear estimation, we revisit data analyses from the Kilo-Degree Survey (KiDS) using an alternative shape measurement pipeline that is more robust to uncertainties in the calibration. To this end, we present an implementation of =0.789_ and compare its performance to that of łensfit, which has been used in previous data analyses. We find that the multiplicative bias is reduced, in particular for the most distant redshifts, as derived from multi-band image simulations designed to match the KiDS data. For all tomographic bins, we obtain a multiplicative bias $|m|<0.017$, with negligible additive bias. Importantly, the calibration has a negligible sensitivity to key galaxy properties. The resulting robust shear estimates were used to obtain cosmological parameter constraints. We find that the parameter, S_8≡ σ_8 Ω_ /0.3 m -0.024 ^ +0.020 , is consistent with the previous KiDS-1000 łensfit constraint of S_8=0.776^ +0.029 +0.002 _ -0.027-0.003 (statistical and systematic errors). Thanks to the higher effective source density of the catalogue, the constraining power is improved by about 28%. The difference in S_8 with the Planck value remains at a similar level (1.8σ), implying that it is not caused by the shear measurements.