Description
Evaluation of baryonic feedback systematics and mitigation strategy: Insights from HSC-Y3 cosmic shear and prospects for HSC final year analysis and stage IV surveys
Cosmic shear is a powerful probe of matter distribution, especially on small scales. Although the small scale data has a high signal-to-noise ratio, accurately modeling matter distribution on these scales is still challenging due to possible contamination from baryonic physics. These baryonic effects have garnered attention as potential contributors to alleviating the S8 tension observed between weak-lensing cosmology and the cosmology inferred from Planck data.
As an alternative to pursuing an accurate or flexible baryonic physics model, our approach involves assessing the performance of a dark matter (DM)-only model prediction. We measured the correlation functions at scales below the fiducial scale cuts, reaching the scales where large k-modes (k ~ 10 h/Mpc) significantly contribute. Using this data, we evaluate the goodness-of-fit of DM-only model predictions. This model can fit the cosmic shear correlation functions measured from the HSC-Y3 data, even at scales below the fiducial scale cuts. The inferred cosmological parameters, especially S8, are not significantly biased compared to those from Li et al. (2023), which marginalize over a baryonic physics parameter and apply scale cuts to discard the scales where baryonic physics could largely affect the signal. From these findings, we conclude that we do not find a clear signature of baryonic effects in the HSC-Y3 cosmic shear data, considering its associated uncertainties. We further discuss the possibility of distinguishing an extreme baryonic effect for HSC final-year data and the Stage IV surveys such as Roman, LSST, and Euclid. Thanks to the statistical power of those future surveys, we will be able to reject an extreme feedback scenario at high significance using the cosmic shear data on small scales.
Finally, we present the strategy for mitigating the baryonic feedback systematics in the upcoming HSC final-year cosmic shear analysis.
