Accuracy of environmental tracers and consequences for determining the Type Ia supernova magnitude step

Type Ia Supernovae (SNe Ia) are standardizable candles that allow us to measure the recent expansion rate of Universe. Due uncertainties in progenitor physics, potential astrophysical dependencies may bias cosmological measurements if not properly accounted for. The dependency intrinsic luminosity SNe with their host-galaxy environment is often used standardize and commonly parameterized as a step function. This functional form implicitly assumes two-populations Ia. In literature, multiple environmental indicators have been considered, finding different, sometimes incompatible, function amplitudes. We compare these context model, based on ability distinguish two populations. show local H α -based specific star formation (lsSFR) global stellar mass better tracers than, for instance, host galaxy morphology. tracer accuracy can explain discrepancy between observed amplitudes found literature. Using lsSFR or identify populations all other observations, though favoured. As strongly connected age, our results favour prompt delayed population model. any case, there exists differ standardized magnitude by at least 0.121 ± 0.010 mag.