Matter power spectrum reconstruction with KiDS-Legacy: Improved internal ΛCDM consistency and preference for strong baryonic feedback

Direct measurements of the matter power spectrum, Pm(k, z), provide a powerful tool for investigating the observed tensions between models of structure growth, while also testing the internal consistency of cosmological probes. We analysed the cosmic shear data from the final data release of the Kilo-Degree Survey (KiDS), and present a deprojected Pm(k, z), measured in up to three redshift bins. Compared to analyses using previous KiDS releases, we find improved internal consistency in the z ≲ 0.7 regime. At large scales, k ≲ 0.1 h Mpc−1, our power spectrum reconstruction aligns with ΛCDM predictions with a density fluctuation amplitude σ8 = 0.81. Furthermore, at small scales, k = 3–20 h Mpc−1, the average matter power spectrum is suppressed by 30%±10% (stat.) ± 4% (sys.) with 2.8σ significance relative to a dark matter-only model, consistent with expectations of strong baryonic feedback.