Evidence for Evolution or Bias in Host Extinctions of High Redshift Supernovae

High redshift supernova magnitudes of current interest are reexamined. The magnitudes conventionally reported include an additive parameter called the extinction coefficient. We find that the extinction coefficients of a popular “gold” set are well correlated with the deviation of magnitudes from standard Hubble diagrams. The statistical significance of the extinction-acceleration correlation has a random chance probability of less than one in a million. The sense of correlation tends to produce dimming. We discuss related features of the data and potential explanations for the phenomenon including evolution and bias. The hypothesis that extinction coefficients should be corrected empirically provides substantially improved fits to both accelerating and non-accelerating models, with the independent feature of eliminating any significant correlation of residuals.