Impact of Baryonic Processes on Weaklensing Cosmology: Power Spectrum, Nonlocal Statistics, and Parameter Bias
Abstract
We study the impact of baryonic physics on cosmological parameter estimation with weaklensing surveys. We run a set of cosmological hydrodynamics simulations with different galaxy formation models. We then perform raytracing simulations through the total matter density field to generate 100 independent convergence maps with a field of view of 25 {{deg }^{2}}, and we use them to examine the ability of the following three lensing statistics as cosmological probes: power spectrum (PS), peak counts, and Minkowski functionals (MFs). For the upcoming widefield observations, such as the Subaru Hyper SuprimeCam (HSC) survey with a sky coverage of 1400 {{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 baryonic processes such as gas cooling and stellar feedback. When we use PS, peak counts, and MFs, the magnitude of relative bias in the dark energy equation of state parameter w is at a level of, respectively, δ w∼ 0.017, 0.061, and 0.0011. For the HSC survey, these values are smaller than the statistical errors estimated from Fisher analysis. The bias could be significant when the statistical errors become small in future observations with a much larger survey area. We find that the bias is induced in different directions in the parameter space depending on the statistics employed. While the twopoint statistic, i.e., PS, yields robust results against baryonic effects, the overall constraining power is weak compared with peak counts and MFs. On the other hand, using one of peak counts or MFs, or combined analysis with multiple statistics, results in a biased parameter estimate. The bias can be as large as 1σ for the HSC survey and will be more significant for upcoming widerarea surveys. We suggest to use an optimized combination so that the baryonic effects on parameter estimation are mitigated. Such a “calibrated” combination can place stringent and robust constraints on cosmological parameters.
 Publication:

The Astrophysical Journal
 Pub Date:
 June 2015
 DOI:
 10.1088/0004637X/806/2/186
 arXiv:
 arXiv:1501.02055
 Bibcode:
 2015ApJ...806..186O
 Keywords:

 cosmological parameters;
 cosmology: theory;
 gravitational lensing: weak;
 largescale structure of universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 16 pages, 12 figures, ApJ in press