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Title: The relationship between type Ia supernovae and their host galaxies
Author: Pan, Yen-Chen
ISNI:       0000 0004 5354 6074
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2014
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This thesis studies the relationship between type Ia supernovae (SNe Ia) and their host galaxies. The sample consists of 527 SNe Ia with redshift z<0.09 discovered by the Palomar Transient Factory (PTF). We obtained high-quality photometric and spectroscopic data of the host galaxies and determined their stellar mass Mstellar, star formation rate (SFR), gas-phase/stellar metallicity, stellar age and SN offset. In the first part of the analysis, we compare the SN Ia photometric properties to the host parameters. Strong correlations between the SN Ia light-curve width (stretch) and the host age/mass/metallicity are found: fainter, faster-declining events tend to be hosted by older/massive/metal-rich galaxies. There is also some evidence that redder SNe Ia explode in higher metallicity galaxies. SNe Ia in higher-mass/metallicity galaxies also appear brighter after stretch/colour corrections than their counterparts in lower mass hosts, and the stronger correlation is with gas-phase metallicity suggesting this may be the more important variable. We also compare the host stellar mass distribution to that in galaxy targeted SN surveys and the high-redshift untargeted Supernova Legacy Survey (SNLS). The difference between each stellar mass distribution can be explained by an evolution in the galaxy stellar mass function, coupled with a SN delay-time distribution proportional to t-1. Finally, we found no significant difference in the mass-metallicity relation of our SN Ia hosts compared to field galaxies, suggesting any metallicity effect on the SN Ia rate is small. In the second part of the analysis, we compare the SN spectral features to the host parameters. We find that SNe Ia with higher Si ii λ6355 velocities tend to explode in more massive galaxies. We study the strength of the high-velocity component of the Ca ii NIR absorption, and find that SNe Ia with a stronger high-velocity component are preferentially hosted by galaxies with a low Mstellar, a blue colour, and a high SFR, and are therefore likely to arise from the youngest progenitor systems. When combined with other studies, our results support the scenario that these high-velocity features are related to an interaction between the SN ejecta and a circumstellar medium (CSM) local to the SN.
Supervisor: Hook, Isobel; Sullivan, Mark Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Astrophysics ; distance scale ; supernova ; cosmology