Power spectrum covariance of weak gravitational lensing

Weak gravitational lensing observations probe the spectrum and evolution of density fluctuations and the cosmological parameters that govern them. At low redshifts, the nonlinear gravitational evolution of large-scale structu re produces a non-Gaussian covariance in the shear power spectrum measureme nts that affects their translation into cosmological parameters. Using the dark matter halo approach, we study the covariance of binned band power spe ctrum estimates and the four-point function of the dark matter density fiel d that underlies it. We compare this semianalytic estimate to results from N-body numerical simulations and find good agreement. We find that for a su rvey out to z similar to 1, the power spectrum covariance increases the err ors on cosmological parameters determined under the Gaussian assumption by about 15%.