KiDS-450: testing extensions to the standard cosmological model

We test extensions to the standard cosmological model with weak gravitational lensingtomography using 450 deg2 of imaging data from the KiloDegree Survey (KiDS). In these extended cosmologies, which include massive neutrinos, nonzero curvature, evolving dark energy, modified gravity, and running of the scalar spectral index, we also examine the discordance between KiDS and cosmic microwave background measurements from Planck. The discordance between the two datasets is largely unaffected by a more conservative treatment of the lensing systematics and the removal of angular scales most sensitive to nonlinear physics. The only extended cosmology that simultaneously alleviates the discordance with Planckand is at least moderately favoured by the data includes evolving dark energywith a time-dependent equation of state (in the form of the w w 0 − w w a parameterization). In this model, the respective S 8 =σ 8 Ω m /0.3 − − − − − − √ S8=σ8Ωm/0.3 constraints agree at the 1σ level, and there is ‘substantial concordance’ between the KiDS and Planckdatasets when accounting for the full parameter space. Moreover, the Planckconstraint on the Hubble constant is wider than in ΛCDM and in agreement with the Riess et al. (2016) direct measurement of H0. The dark energymodel is moderately favoured as compared to ΛCDM when combining the KiDS and Planckmeasurements, and marginalized constraints in the w w 0 − w w a plane are discrepant with a cosmological constant at the 3σ level. KiDS further constrains the sum of neutrino masses to 4.0 eV (95% CL), finds no preference for time or scale dependent modifications to the metric potentials, and is consistent with flatness and no running of the spectral index.