GALICS: A direct link between theory and observations

This contribution advocates a new method for comparing theoretical predictions to observations. Properties of virtual galaxies are computed using the hybrid model for hierarchical galaxy formation GALICS (for Galaxies In Cosmological Simulations), which takes advantage of large cosmological N-body simulations to plug in simple semi-analytic recipes describing the fate of the baryons. From such a fake galaxy catalog, one can build light cones, and project them onto virtual CCD devices, taking into account the technical characteristics of the detector/telescope. As a result, realistic mock images can be produced, which can then be directly compared to real observations. This revised version was published online in August 2006 with corrections to the Cover Date.