Pantheon + supernovae corrected for progenitor age indicate the universe is decelerating

Abstract

We examine the impact of progenitor age-dependent luminosity evolution of Type Ia supernovae on a cosmographic measurement of the deceleration parameter (Formula presented). Our recent redshift tomographic analysis showed that locally (Formula presented) has a strong dipole anisotropy aligned approximately with the bulk flow, and only a small monopole component remains at distances exceeding a few hundred Mpc. Applying redshift-dependent corrections for progenitor age to the Pantheon + catalogue, we find that this shifts the monopole component of (Formula presented) to positive values (i.e. deceleration) while leaving the local dipole component essentially unchanged.