Orateur
Description
Measurements of the standardisable type Ia supernova (SNeIa) out to the earliest epochs in the Universe remain the most robust probe of cosmic acceleration. However, to ensure unbiased precision estimates on the nature of dark energy requires a firm understanding of where the observed 0.15mag dispersion observed in these events originates from, and a detailed description of any evolution in their mean properties with redshift. With correlations between the observed properties of SNeIa and their local environment now routinely used in SNIa standardisation but not physically motivated, characterising this effect is key to ensure that the inferred cosmological parameters are not plagued by systematic uncertainties.
Using just 10% of the Dark Energy Survey Supernova Program (DES-SN) dataset, we have shown that SNeIa in high mass galaxies are intrinsically more luminous (after correction) than their low mass counterparts, but that the magnitude of this difference relies strongly upon assumptions used in determining the distance to each SN. This is a consequence of intrinsic correlations between SN light-curve width and colour, and host galaxy properties, which, if incorrectly modelled, can lead to biases in the estimates distances and hence the cosmological parameters. In this talk I shall extend this analysis, utilising the full DES-SN sample to studying the standardisation of SNeIa with regards to their host galaxy environment. With significant attention focused around how SNIa host properties can be used to improve cosmological constraints from SNe, I will highlight how a subsample of events, solely found in low luminosity environments can maximise our understanding of dark energy from SN, but how incorrectly accounting for contamination and population drift can severely bias the inferred cosmological parameters. With LSST just around the corner, DES-SN presents the ideal test-bed to constrain the correlation between galaxy properties and SNIa luminosity: critical to ensure that our understanding of dark energy is unbiased.
