Cosmic Microwave Background Anisotropies from the Rees-Sciama Effect in Omega 0 <=1 Universes

We investigate the imprint of nonlinear matter condensations on the cosmic microwave background (CMB) in Ω₀ < 1 cold dark matter (CDM) model universes with simulation domains ranging from 120 h⁻¹ Mpc to 360 h⁻¹ Mpc in size. We concentrate on the secondary temperature anisotropies induced by time varying gravitational potentials occurring after decoupling. Specifically, we investigate the importance of the Rees-Sciama effect due to: (1) intrinsic changes in the gravitational potential of forming, nonlinear structures; (2) proper motion of nonlinear structures; and (3) late-time decay of gravitational potential perturbations in open universes. CMB temperature anisotropies are obtained by numerically evolving matter inhomogeneities and CMB photons from an early, linear epoch (z = 100) to the present, nonlinear epoch (z = 0). We test the dependence and relative importance of these secondary temperature anisotropies as a function of the scale of the underlying matter (voids, superclusters) and as a function of Ω₀. The results of the Ω₀ < 1 models are compared to a similarly executed = 1 simulation. We find that in low-density models all three sources of anisotropy can be relevant, reaching levels of ΔT/T 10⁻⁶. We also find that, for Ω₀ < 1, at large scales the secondary temperature anisotropies are dominated by the decaying potential.