Type Ia Supernova Magnitude Step from the local Dark Matter Environment

Understand

Residuals in the Hubble diagram at optical wavelengths and host galaxy stellar mass are observed to correlate in Type Ia supernovae (SNe Ia) (`magnitude step').

• Among possible progenitor channels for the associated explosions, those based on dark matter (DM) have attracted significant attention, including our recent proposal that `normal' SNe Ia from bare detonations in sub-Chandrasekhar white dwarf stars are triggered by the passage of asteroid-mass primordial black holes (PBHs): the magnitude step could then originate from a brightness dependence on stellar properties, on DM properties, or both.
• Here, we present a method to estimate the local DM density and velocity dispersion of the environment of SN Ia progenitors.
• We find a luminosity step of $0.52\pm 0.11\,$mag corresponding to bins of high vs low DM density in a sample of 222 low-redshift events from the Open Supernova Catalog.