Dynamic or Systematic? Bayesian model selection between dark energy and supernova biases

Abstract DES-5Y supernovae, combined with DESI BAO, appear to favour Chevallier–Polarski–Linder (w0, wa) dynamical dark energy over ΛCDM. It has been suggested in other work that this is driven by a systematic in the DES pipeline, which particularly affects the low-redshift supernovae brought in from legacy surveys. It is difficult to investigate these data in isolation, however, as the complicated supernovae pipelines must properly account for selection effects. In this work, we discover that a