PoS(CMB2006)058 Ray-tracing through N-body simulations and CMB anisotropy estimations Diego Sáez ∗ and Neus Puchades Dpto. de Astronomía y Astrofísica, Universidad de Valencia E-mail: diego.saez@uv.es José V. Arnau Dpto. de Matemática Aplicada, Universidad de Valencia Marius J. Fullana Institut de Matemàtica Multidisciplinar, Universitat Politècnica de València The fully nonlinear evolution of galaxy clusters and substructures –given by N-body simulations– is used to simulate maps of the Rees-Sciama (RS) effect. The universe is covered by simulation boxes and photons move across them. A recent technique for ray-tracing through N-body simu- lations is described in detail and implemented. It is based on the existence of preferred directions (to move photons through the boxes), and also on the use of an appropriate cutoff. By the moment, only small RS maps (around 2 ◦ × 2 ◦ ) have been obtained with this technique. We justify that our ray-tracing procedure is also appropriate in the case of large simulation cubes (∼ 1000 Mpc per edge), where high enough resolutions can be obtained with appropriate N-body codes and modern computers. CMB and Physics of the Early Universe 20-22 April 2006 Ischia, Italy ∗ Speaker. c  Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. http://pos.sissa.it/