Cosmology from cosmic shear power spectra with Subaru Hyper Suprime-Cam first-year data

TL;DR

This paper presents a high-precision measurement of cosmic shear power spectra from Subaru HSC first-year data, constraining cosmological parameters with careful uncertainty analysis and comparison to Planck results.

Contribution

First-year Subaru HSC cosmic shear analysis providing high-significance measurements and detailed systematic uncertainty treatment for cosmological parameter estimation.

Findings

Measured $S_8$ with ~3% precision

Results slightly favor lower $S_8$ than Planck

Systematic errors can shift $S_8$ by ~0.6$\sigma$

Abstract

We measure cosmic weak lensing shear power spectra with the Subaru Hyper Suprime-Cam (HSC) survey first-year shear catalog covering 137deg$^2$ of the sky. Thanks to the high effective galaxy number density of $\sim$17 arcmin$^{-2}$ even after conservative cuts such as magnitude cut of $i<24.5$ and photometric redshift cut of $0.3\leq z \leq 1.5$, we obtain a high significance measurement of the cosmic shear power spectra in 4 tomographic redshift bins, achieving a total signal-to-noise ratio of 16 in the multipole range $300 \leq \ell \leq 1900$. We carefully account for various uncertainties in our analysis including the intrinsic alignment of galaxies, scatters and biases in photometric redshifts, residual uncertainties in the shear measurement, and modeling of the matter power spectrum. The accuracy of our power spectrum measurement method as well as our analytic model of the covariance matrix are tested against realistic mock shear catalogs. For a flat $\Lambda$ cold dark matter ($\Lambda$CDM) model, we find $S_8\equiv \sigma_8(\Omega_{\rm m}/0.3)^\alpha=0.800^{+0.029}_{-0.028}$ for $\alpha=0.45$ ($S_8=0.780^{+0.030}_{-0.033}$ for $\alpha=0.5$) from our HSC tomographic cosmic shear analysis alone. In comparison with Planck cosmic microwave background constraints, our results prefer slightly lower values of $S_8$, although metrics such as the Bayesian evidence ratio test do not show significant evidence for discordance between these results. We study the effect of possible additional systematic errors that are unaccounted in our fiducial cosmic shear analysis, and find that they can shift the best-fit values of $S_8$ by up to $\sim 0.6\sigma$ in both directions. The full HSC survey data will contain several times more area, and will lead to significantly improved cosmological constraints.