UC Berkeley

Type Ia supernovae (SNe Ia) have been used successfully to derive constraints on the expansion history of our universe. They are also a source of kinetic energy and iron-group elements in galaxies, and they are inherently interesting cosmic events whose study requires the application of sophisticated algorithms and computational architectures. Late-time, or nebular, observations of SNe Ia are taken during the phase in which the ejecta are optically thin and are heated by radioactive decay of iron-group elements. They are a powerful and unique probe of ejecta properties and may be used to infer information about the explosion itself. In this thesis, I present a three-dimensional radiative transfer code to calculate the properties and synthetic data of optically thin, homologously-expanding gases illuminated by radioactive decay energy and apply it to a variety of SN Ia explosion models. I derive the relationship between key explosion properties and nebular spectra using a suite of parametrized models, which results in the identification of a number of degeneracies. I also present the first-ever multidimensional nebular spectra of SNe Ia interacting with a binary companion, which leads us to rule out classic single-degenerate systems as SN Ia progenitors.