KiDS-Legacy: Constraining dark energy, neutrino mass, and curvature

Abstract

We constrained minimally extended cosmological models with the cosmic shear analysis of the final data release from the Kilo-Degree Survey (KiDS-Legacy) in combination with external probes. Due to the consistency of the KiDS-Legacy analysis with the cosmic microwave background (CMB), we could combine these datasets reliably for the first time. Additionally, we used CMB lensing, galaxy redshift-space distortions, and baryon acoustic oscillations. We assessed, in turn, the effects of spatial curvature, varying neutrino masses, and an evolving dark energy component on cosmological constraints from KiDS-Legacy alone and from KiDS-Legacy combined with external probes. We find KiDS-Legacy to be consistent with the fiducial flat $\hat{I}›$-cold dark matter ($\hat{I}›$CDM) analysis with $c^2\sum m_{\hat{I}}½\le 1.5$eV, $w_0=-1.0\pm 0.7$, and $w_a=-1.3_{-2.0}^{+1.9}$ while $\hat{I}{\text{c◯}}_K=0.08_{-0.17}^{+0.16}$ (1$\ddot{I}ƒ$ bounds) with an almost equal goodness of fit. The $w_0{w}_a$CDM model is not a significant improvement over $\hat{I}›$CDM when cosmic shear and CMB lensing are combined, yielding a Bayes factor $B=0.07$. If all probes are combined, however, $B$ increases to 2.73, corresponding to a $2.6\ddot{I}ƒ$ suspiciousness tension. The constraint on $S_8=\ddot{I}{ƒ}_8\sqrt{\hat{I}{\text{c◯}}_{\mathrm{m}}/0.3}$ is robust to opening up the parameter space for cosmic shear. Adding all external datasets to KiDS-Legacy, we find $S_8=0.816\pm 0.006$ in $\hat{I}›$CDM and $S_8=0.837\pm 0.008$ in $w_0{w}_a$CDM for all probes combined.

14 pages, 8 figures, published in A&A

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