IMPACT OF BARYONIC PROCESSES ON WEAK-LENSING COSMOLOGY: POWER SPECTRUM, NONLOCAL STATISTICS, AND PARAMETER BIAS

Abstract

We study the impact of baryonic physics on cosmological parameter estimation with weak lensing surveys. We run a set of cosmological hydrodynamics simulations with different galaxy formation models. We then perform ray-tracing simulations through the total matter density field to generate 100 independent convergence maps of 25 ${\rm deg}^2$ field-of-view, and use them to examine the ability of the following three lensing statistics as cosmological probes; power spectrum, peak counts, and Minkowski functionals. For the upcoming wide-field observations such as Subaru Hyper Suprime-Cam (HSC) survey with a sky coverage of 1400 ${\rm deg}^2$, these three statistics provide tight constraints on the matter density, density fluctuation amplitude, and dark energy equation of state, but parameter bias is induced by the baryonic processes such as gas cooling and stellar feedback. The bias can be significant when the statistical errors become small in future observations with a much larger survey area. We find the bias is induced in different directions in the parameter space depending on the statistics employed. While the two-point statistic, i.e. power spectrum, yields robust results against baryonic effects, the overall constraining power is weak compared with peak counts and Minkowski functionals. On the other hand, using one of peak counts or Minkowski functionals, or combined analysis with multiple statistics, results in biased parameter estimate. The bias can be as large as $1\sigma$ for HSC survey, and will be more significant for upcoming wider area surveys. We suggest to use an optimized combination so that the baryonic effects on parameter estimation are mitigated. Such `calibrated' combination can place stringent and robust constraints on cosmological parameters.