Implications of two type IA supernova populations for cosmological measures

Recent work suggests that Type Ia supernovae (SNe) are composed of two distinct populations: prompt and delayed. By explicitly incorporating properties of host galaxies, it may be possible to target and eliminate systematic differences between the putative prompt and delayed populations. However, any resulting post-calibration shift in luminosity between the components will cause a redshift-dependent systematic shift in the Hubble diagram. Utilizing an existing sample of 192 SNe, they find that the post-calibration average luminosity difference between prompt and delayed SNe is constrained to be (4.5 {+-} 8.9)%. If the absolute magnitude difference between the two populations is 0.025 and ignored when fitting for cosmological parameters with 2300 SNe, then the dark energy equation of state (EOS) is biased around 0.9{sigma}. This bias is reduced once the systematic effect is marginalized over, but with an increase in the uncertainty of the EOS. In the case no prior on the two population systematic is introduced, the EOS uncertainty is increased by a factor of 2.5 from that without the two population systematic effect in the SNe sample.