Master thesis defense by Lucas Hallgren

Constraining properties of Type Ia supernovae and host galaxy extinction from Bayesian hierarchical modelling of observations from the Zwicky Transient Factory survey

Abstract

Standardisation of Type Ia supernovae is an important field of investigation to constrain parameters of the physical model describing the evolution of our Universe as a whole. In this project we constrain intrinsic properties of supernovae populations along with extrinsic properties related to their origin environment of host galaxy extinction. With observational photometric light curve data from over 700 Type Ia supernovae combined with measured host galaxy stellar mass and colour, globally and locally, from the Zwicky Transient Factory survey, we perform Bayesian hierarchical modelling to constrain hyperparameters describing the latent variables of the standardisation model.

We perform a supernova multi-population investigation having 3 distinct supernova populations in our best fit model, which can be used to disentangle and explain the true differences in the intrinsic supernova properties and the extrinsic origin environments that differ from population to population.

We draw relations between properties of the supernova populations best fit values to host galaxy characteristics such as age, stellar environment, and dust content, and intrinsic progenitor channels of the supernova explosion, and we discuss how the choice of prior distributions of variables in the population-dependent standardisation affect the outcome of results. Finally, we discuss the possible need of further and a more complex investigation of individual prior distributions regarding intrinsic SN colour and reddening due to dust, which both contributes to the observed colour of the supernova.

Censor

Hans Kjeldsen