Training custom light curve models of SN Ia subpopulations selected according to host galaxy properties

• DOI: 10.1093/mnras/stae293
• Publication Date: 2024-01-30T17:52:23Z
• Authors: G Taylor; C Lidman; B Popovic; H J Abbot
• Keywords: Spectral energy distribution; Absolute magnitude

ABSTRACT Type Ia supernova (SN Ia) cosmology analyses include a luminosity step function in their distance standardization process to account for an observed yet unexplained difference the post-standardization luminosities of SNe originating from different host galaxy populations [e.g. high-mass ($M \gtrsim 10^{10} \, {\rm M}_{\odot }$) versus low-mass galaxies]. We present novel method including host-mass correlations SALT3 (Spectral Adaptive Light curve Template 3) light model used standardizing SN distances. split training sample according host-mass, independent models low- and high-host-mass samples. Our indicate that there are average Si ii spectral feature strengths between two populations, energy distribution galaxies is bluer than counterpart. then use our trained perform analysis on 3-yr spectroscopically confirmed Dark Energy Survey sample, treating as separate throughout. find mass-split reduce Hubble residual scatter albeit at low statistical significance. do reduction mass-correlated but conclude this arises model-dependent re-definition fiducial absolute magnitude rather themselves. results stress importance adopting standard definition parameters (x0, x1, c) order extract most value out modelling tools currently available correctly interpret fit with models.