Type Ia supernovae: Exposing models to observations

Type Ia supernovae play an important role in observational cosmology and in various astrophysical processes. As main producers of iron group elements, they are a key component in the cosmic cycle of matter. The questions about the nature of the progenitor systems from which these cosmic explosions arise and of their physical mechanism, however, are not settled. Several possibilities have been suggested in the literature. We discuss recent developments and present multidimensional explosion simulations referring to two different scenarios. Combined with detailed radiative transfer calculations that predict observables from the models and allow direct comparison with astronomical data, these simulations shed light on the nature of the progenitor systems. Although the range of observed properties is large enough to accommodate many theoretical explosion models, it is particularly important to identify the class of objects that constitutes the bulk of Type Ia supernovae. Even when starting out from systems as diverse as Chandrasekhar-mass white dwarfs and double white dwarf mergers, there is some degeneracy in the predicted observables that prevents a straightforward judgement on the validity of the models. We discuss possible ways to overcome this problem and to discriminate between different scenarios.