  We compare models for Type Ia supernova (SN Ia) light curves and spectra with
an extensive set of observations. The models come from a recent survey of 44
two-dimensional delayed-detonation models computed by Kasen, Roepke & Woosley
(2009), each viewed from multiple directions. The data include optical light
curves of 251 SNe Ia and 2231 low-dispersion spectra from the Center for
Astrophysics, plus data from the literature. The analysis uses standard
techniques employed by observers, including MLCS2k2, SALT2, and SNooPy for
light-curve analysis, and the Supernova Identification (SNID) code of Blondin &
Tonry for spectroscopic comparisons to assess how well the models match the
data. We show that the models that match observed spectra best lie
systematically on the observed width-luminosity relation. Conversely, we reject
six models with highly asymmetric ignition conditions and a large amount (>1
M_sun) of synthesized 56Ni that yield poor matches to observed SN Ia spectra.
More subtle features of the comparison include the general difficulty of the
models to match the U-band flux at early times, caused by a hot ionized ejecta
that affect the subsequent redistribution of flux at longer wavelengths. We
examine ways in which the asymptotic kinetic energy of the explosion affects
both the predicted velocity and velocity gradient in the Si II and Ca II lines.
Models with an asymmetric distribution of 56Ni are found to result in a larger
variation of photometric and spectroscopic properties with viewing angle,
regardless of the initial ignition setup. We discuss more generally whether
highly anisotropic ignition conditions are ruled out by observations, and how
detailed comparisons between models and observations involving both light
curves and spectra can lead to a better understanding of SN Ia explosion
mechanisms.
