Cosmological constraints from weak lensing scattering transform using HSC Y1 data

As weak lensing surveys go deeper, there is an increasing need for reliable characterization of non-Gaussian structures at small angular scales. Here we present the first cosmological constraints with weak lensing scattering transform, a statistical estimator that combines efficiency, robustness, and interpretability. With the Hyper Suprime-Cam survey (HSC) year 1 data, we obtain Ωm = 0.29-0.03+0.04, SS8 ≡ σ8(Ωm/0.3)0.5 = 0.83±0.02, and intrinsic alignment strength AIA = 1.0±0.4 through simulation-based forward modeling. Our constraints are consistent with those derived from Planck. The error bar of Ωm is 2 times tighter than that obtained from the power spectrum when the same scale range is used. This constraining power is on par with that of convolutional neural networks, suggesting that further investment in spatial information extraction may not yield substantial benefits. We also point out an internal tension of S8 estimates linked to a redshift bin around z ∼ 1 in the HSC data. We found that discarding that bin leads to a consistent decrease of S8 from 0.83 to 0.79, for all statistical estimators. We argue that photometric redshift estimation is now the main limitation in the estimation of S8 using HSC. This limitation is likely to affect other ground-based weak lensing surveys reaching redshifts greater than one. Alternative redshift estimation techniques, like clustering redshifts, may help alleviate this limitation.