Master Thesis Defense by Jacob Osman Hjortlund
Title: Exploring Demographic Drift of Type Ia SNe and its Impact on Cosmology
Abstract:
Type Ia supernovae (SNe) have played a significant role in measuring the acceleration of the Universe’s expansion and the existence of dark energy. However, understanding the nature of SNe and the impact of population, originating from two distinct progenitor channels (single- and double-degenerate), changes over cosmic time is crucial to accurately measuring these phenomena. In this talk, we present a novel Bayesian hierarchical two-population model of Type Ia SNe which enables us to measure the properties of the two populations, redshift evolution of their relative fractions and thus investigate the impact of these elements on the precision and accuracy of constraints on the cosmological parameters. Our model builds on earlier work by accounting for the varying fraction of two distinct Type Ia supernova populations over cosmic time. By modeling the redshift dependence of the two populations, we can estimate their respective fractions at differ- ent epochs and explore the impact of these changes on measurements of cosmological parameters. We apply our model to simulations and observational data from Pantheon+. We show that observational data has signatures of redshift dependent fractions of the supernova populations and discuss these results in the framework of basic expectations related to the star formation history. We find that this demographic drift has potential implications for measuring cosmological parameters, as it affects the derived distance and intrinsic properties of Type Ia SN. We discuss the implications of our results for future observations and the study of cosmology. Our model provides a framework for incorporating demographic drift into the two population model of Type Ia SNe, which could lead to more accurate measurements of the properties of dark energy. We also highlight the importance of continued observational efforts to constrain the properties of Type Ia SNe and their progenitor scenarios. In conclusion, our Bayesian two-population model of Type Ia SNe provides a powerful tool for exploring the demographic drift of these populations and its implications for measuring cosmological parameters. By accounting for the changing fraction of the two populations over cosmic time, we can improve our understanding of the nature of Type Ia SNe and their use as cosmological probes.
Supervisor:
- Radek Wojtak, University of Copenhagen, Niels Bohr Institute
Censor:
- Hans Kjeldsen, Aarhus University
Post Defense Reception to be held at: DARK Lunch Room - NBB, G1