Smarter redshift estimates nudge weak lensing closer to Planck

Using a template-based Bayesian hierarchical model applied to the KiDS+VIKING-450 weak lensing survey, this analysis infers photometric redshift distributions by marginalizing over uncertainty rather than fixing them beforehand. Principal component analysis distills a compact set of representative spectral templates, keeping the calculation computationally feasible with subsets of 100,000 galaxies. The result is S8 = 0.756 ± 0.039, somewhat higher than previous KiDS analyses, shrinking the disagreement with Planck to under 2σ. The work suggests that how redshift distributions are modeled—not just measured—meaningfully affects cosmological conclusions from lensing surveys.