Baryonic effects on weak-lensing two-point statistics and its cosmological implications

We develop an extension of the Halo Model that describes analytically the corrections to the matter power spectrum due to the physics of baryons. We extend these corrections to the weak-lensing shear angular power spectrum. Within each halo, our baryonic model accounts for: 1) a central galaxy, the major stellar component whose properties are derived from abundance matching techniques; 2) a hot plasma in hydrostatic equilibrium and 3) an adiabatically-contracted dark matter component. This analytic approach allows us to compare our model to the dark-matter-only case. Our basic assumptions are tested against the hydrodynamical simulations of Martizzi et. al. (2014), with which a remarkable agreement is found. Our baryonic model has only one free parameter, M ₂ₑ₈ₓ, the critical halo mass that marks the transition between feedback-dominated halos, mostly devoid of gas, and gas rich halos, in which AGN feedback effects become weaker. We explore the entire cosmological parameter space, using the angular power spectrum in three redshift bins as the observable, assuming a Euclid-like survey. We derive the corresponding constraints on the cosmological parameters, as well as the possible bias introduced by neglecting the effects of baryonic physics. We find that, up to ₌₀ₗ=4000, baryonic physics plays very little role in the cosmological parameters estimation. However, if one goes up to ₌₀ₗ=8000, the marginalized errors on the cosmological parameters can be significantly reduced, but neglecting baryonic physics can lead to bias in the recovered cosmological parameters up to 10σ. These biases are removed if one takes into account the main baryonic parameter, M ₂ₑ₈ₓ, which can also be determined up to 1-2\%, along with the other cosmological parameters.