KiDS+VIKING-450: Cosmic shear tomography with optical+infrared data
  We present a tomographic cosmic shear analysis of the Kilo-Degree Survey
(KiDS) combined with the VISTA Kilo-Degree Infrared Galaxy Survey (VIKING).
This is the first time that a full optical to near-infrared data set has been
used for a wide-field cosmological weak lensing experiment. This unprecedented
data, spanning $450~$deg$^2$, allows us to improve significantly the estimation
of photometric redshifts, such that we are able to include robustly
higher-redshift sources for the lensing measurement, and - most importantly -
solidify our knowledge of the redshift distributions of the sources. Based on a
flat $\Lambda$CDM model we find $S_8\equiv\sigma_8\sqrt{\Omega_{\rm
m}/0.3}=0.737_{-0.036}^{+0.040}$ in a blind analysis from cosmic shear alone.
The tension between KiDS cosmic shear and the Planck-Legacy CMB measurements
remains in this systematically more robust analysis, with $S_8$ differing by
$2.3\sigma$. This result is insensitive to changes in the priors on nuisance
parameters for intrinsic alignment, baryon feedback, and neutrino mass. KiDS
shear measurements are calibrated with a new, more realistic set of image
simulations and no significant B-modes are detected in the survey, indicating
that systematic errors are under control. When calibrating our redshift
distributions by assuming the 30-band COSMOS-2015 photometric redshifts are
correct (following the Dark Energy Survey and the Hyper Suprime-Cam Survey), we
find the tension with Planck is alleviated. The robust determination of source
redshift distributions remains one of the most challenging aspects for future
cosmic shear surveys.
