| Abstract | Context. Type Ia supernova (SNIa) are excellent probes of local distance and the growing sample sizes of SNIa have driven an increased propensity to study the associated systematic uncertainties and improve standardisation methods in preparation for the next generation of cosmological surveys into the dark energy equation of state, w.
Aims. We aim to probe the potential change in the SNIa standardisation parameter, c, with redshift and the host-galaxy of the supernova. Improving the standardisation of SNIa brightness measurements will require the relationship between the host and the SNIa to be accounted for. In addition, potential shifts in the SNIa standardisation parameters with redshift will cause biases in the recovered cosmology.
Methods. In this work, we assembled a volume-limited sample of 3000 likely SNIa across a redshift range from z = 0.015 to z = 0.36. This sample was fitted with changing mass and redshift bins to determine the relationship between the intrinsic properties of SNe Ia and their redshift and host galaxy parameters. We then investigated the colour-luminosity parameter, β, as a subsequent test of the SNIa standardisation process.
Results. We find that the changing colour distribution of SNe Ia with redshift is driven by dust at a confidence of > 4σ. Additionally, we show a strong correlation between the host galaxy mass and the colour-luminosity coefficient β (> 4σ), even when accounting for the quantity of dust in a host galaxy.
Conclusions. These results indicate that the observed colour distribution of SNe Ia does change with redshift. However, we note that this is an observational effect, rather than an intrinsic change. Future cosmological measurements with SNe Ia must take into account these changing dust distributions to reduce the number of potential sources of systematic uncertainty. |
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