Cosmic shear with small scales: DES-Y3, KiDS-1000 and HSC-DR1

Abstract We present a cosmological analysis of the combination of the DES-Y3, KiDS-1000 and HSC-DR1 weak lensing samples under a joint harmonic-space pipeline making use of angular scales down to ℓ max =4500, corresponding to significantly smaller scales (δθ ~ 2.4') than those commonly used in cosmological weak lensing studies. We are able to do so by accurately modelling non-linearities and the impact of baryonic effects using Baccoemu . We find S 8 ≡ σ 8 √(Ω m /0.3) = 0.795 +0.015 -0.017 , in relatively good agreement with CMB constraints from Planck (less than ~1.8 σ tension), although we obtain a low value of Ω m =0.212 +0.017 -0.032 , in tension with Planck at the ~3σ level. We show that this can be recast as an H 0 tension if one parametrises the amplitude of fluctuations and matter abundance in terms of variables without hidden dependence on H 0 . Furthermore, we find that this tension reduces significantly after including a prior on the distance-redshift relationship from BAO data, without worsening the fit. In terms of baryonic effects, we show that failing to model and marginalise over them on scales ℓ ≲ 2000 does not significantly affect the posterior constraints for DES-Y3 and KiDS-1000, but has a mild effect on deeper samples, such as HSC-DR1. This is in agreement with our ability to only mildly constrain the parameters of the Baryon Correction Model with these data.