| dc.description.abstract | Type Ia Supernovae (SNe Ia) are the most precise distance indicators available for cosmological studies. Utilizing this characteristic in analysis led to the discovery of dark energy and the accelerated expansion of the Universe, and SNe Ia continue to be crucial for understanding modern cosmology. However, there are systematic uncertainties associated with SNe Ia that prevent use of these powerful tools to their full potential. The scatter observed in their standardized magnitudes is larger than can be explained by current knowledge. For example, it is difficult to separate the reddening effects of dust from SN Ia intrinsic color. Upcoming surveys like LSST and Roman will discover an unprecedented number of SNe Ia, shrinking the statistical contribution such that systematic error vastly outweighs statistics. In order to be prepared for these data, it is crucial that sources of systematic error in SN Ia standardization are better understood.
This dissertation concerns the variability among SNe Ia. This includes observational variability, the physical implications of these variations, and their effects on SN Ia cosmology. We find that the “bump” feature of the color-magnitude diagram (CMAGIC) diagram of SNe Ia is strongly correlated with the slope of the subsequent linear region. In addition, the slope and bump feature are correlated with both photometric and spectral parameters that are associated with decline rate. This result may be associated with chemical mixing due to large-scale Rayleigh-Taylor instabilities at the Si/Ni boundary. A preliminary Hubble residual analysis is described, which shows that these features may need to be considered in order to ensure a uniform sample for cosmological studies.
Chapter 2 describes the data used in this work, namely, the Nearby Supernova Factory (SNfactory) spectrophotometric dataset. Chapter 3 describes the analytical procedures used in this work. This includes both photometric and spectroscopic techniques. We focus on color-magnitude intercept calibration (CMAGIC) methods, introduced in Section 1.3, to quantify some aspects of SN Ia diversity. Chapter 4 discusses the results of the analyses described in Chapter 3. CMAGIC-based diversity is discussed in terms of supernova physics, as well as cosmology. Finally, Chapter 5 summarizes the key results of this work, and recommendations for future work are detailed. | |
