Type Ia Supernova Colors and Ejecta Velocities: Hierarchical Bayesian Regression with Non-Gaussian Distributions

Understand

We investigate the statistical dependence of the peak intrinsic colors of Type Ia supernovae (SN Ia) on their expansion velocities at maximum light, measured from the Si II 6355 spectral feature.

• We construct a new hierarchical Bayesian regression model, accounting for the random effects of intrinsic scatter, measurement error, and reddening by host galaxy dust, and implement a Gibbs sampler and deviance information criteria to estimate the correlation.
• The method is applied to the apparent colors from BVRI light curves and Si II velocity data for 79 nearby SNe Ia.
• The apparent color distributions of high (HV) and normal velocity (NV) supernovae exhibit significant discrepancies for B-V and B-R, but not other colors.