Cosmological Simulation of Gravitational Weak Lensing in Flat Models

Abstract

Statistical averages of optical quantities (the convergence, shear and amplification) for ray bundles passing through cosmological inhomogeneities are derived in flat models (the S model with (Ω0, λ0) = (1.0,0) and the L model with (0.2,0.8)). Gravitational weak lensing is analyzed by directly solving null-geodesic equations. The evolution of the spatial mass distribution is given by N-body simulations in a tree-code. In the L model all particles are regarded as equivalent (compact) lens objects with a galactic size and in the S model particles consist of compact lens objects with a galactic size and clouds with weaker lens powers. The compact lens objects in the two models are assumed to have the same mass density. It is found as a result that the ratios of optical quantities in the S model to those in the L model increase with the separation angle (θ) of rays. If θ ∼ 2 arcsec and 360 arcsec, the ratios are ∼ 1.5 and ∼ 2.5, respectively, for sources at z = 1.