Host Galaxy Mass Combined with Local Stellar Age Improve Type Ia Supernovae Distances

Understand

Type Ia supernovae (SNe Ia) are standardizable candles, but for over a decade, there has been a debate on how to properly account for their correlations with host galaxy properties.

• Using the Bayesian hierarchical model UNITY, we simultaneously fit for the SN Ia light curve and host galaxy standardization parameters on a set of 103 Sloan Digital Sky Survey II SNe Ia.
• We investigate the influences of host stellar mass, along with both localized ($r<3$ kpc) and host-integrated average stellar ages, derived from stellar population synthesis modeling.
• We find that the standardization for the light-curve shape ($\alpha$) is correlated with host galaxy standardization terms ($\gamma_i$) requiring simultaneous fitting.