No description available.

No description available.

No description available.

Supernovae (SNe) play an important role in many areas of astrophysics. However, despite years of observational and theoretical research, the exact nature of their progenitor systems remains undetermined. The work presented in this thesis attempts to further our understanding of these explosive events by investigating the nature of the stellar populations in the immediate vicinity of historical events. The research is, in the main based on Ha and R-band observations of a large sample of ~200 host galaxies that have harboured over 230 SNe.

In this thesis I present a detailed study of two type IIn supernovae: PTFll iqb and SN 2011jb. I find that PTFll iqb shows complex Ha and H~ profiles, which indicate that the progenitor underwent multiple periods of mass loss . The shells formed by these periods of mass loss are interacting with the ejecta . The measured widths of the narrow components are consistent with a Red Supergiant progenitor. Asymmetric line profiles at late times suggest dust formation. Contrastingly, SN 2011jb appears to be a type Ic supernova which is interacting with a CSM, similarly to SNe 2002ic and SN 2005gj. In these cases the spectra can be modeled as ejecta interacting with a CSM superimposed upon a type la or le spectrum, which appears weak due to the attenuation caused by the dust. I endeavor to conduct a search of all core-collapse supernovae which have exploded within the cryogenic lifetime of Spitzer, within 25Mpc. It is found that type Un SNe were twice as likely to be recovered as other type II supernovae, but due to the low numbers of type Iblc supernovae for which data exists it is not possible. to draw any conclusions about their likelihood of being recovered. The dust which is found in type II supernovae was likely to be caused by a light echo as the ejecta heated the surrounding circumstellar medium. However, dust formation is found to be an equally likely explanation for the presence of dust in other type II supernovae. Lastly, I discuss approaches for furthering our understanding of core-collapse supernovae. These include plans for discovering supernovae more quickly, and studying them more effectively, using surveys such as PESSTO, and pushing the boundaries for the faintest and furthest supernovae we can see using larger telescopes such as the E- ELT.

In the last fifteen years, searches for the progenitors of core-collapse supernovae (SNe) in archival images have provided the crucial "missing link" between the final stages in the evolution of a massive star, and its explosion as a core-collapse SN. In this thesis, I present new detections and limits for core-collapse SN progenitors, together with a critical re-analysis of those already published. I present detailed studies of the progenitors of three nearby SNe. For the sub- luminous Type IIP SN 2009md, I find a coincident red supergiant progenitor with a mass of ~8 M in archival images, which is consistent with the low mass progenitors found for other faint Type IIP SNe. Such events appear to come from red supergiants at the lower extremum of the mass range for core-collapse. I discuss the intermediate Type IIP /L SN 2009kr, for which I find what appears to be a massive yellow supergiant progenitor. I consider possible explanations for the observed colour of the progenitor candidate at explosion, and the consequences for stellar evolution. I also analyse archival pre-explosion images of the site of the Type Ib SN 2009jf, for which a progenitor was not detected. I attempt to constrain the age of the stellar population in the locale of the SN, and use this to set a limit on the progenitor mass. I also extend the time- and volume-limited sample of core-collapse SNe presented by Smartt et al. (2009). I use this new data, together with an improved re-analysis of the original limits of Smartt et al., to set an upper limit on the mass of Type IIP and Type IIL SN progenitors of 20M, at a 95 per cent confidence level. This limit is lower than the most massive observed red supergiants, providing strong support for suggestions that some of the most massive red supergiants do not produce bright SNe, but rather collapse to form black holes either directly or via fall-back. Finally, I discuss some alternative approaches for understanding core-collapse SNe and their progenitors, including searching for progenitors in X-ray data, a survey for optically faint failed SNe, and a deeper search for a surviving companion to the progenitor of the Galactic SN Cas A.

We present the cosmological analysis of 752 photometrically-classified Type Ia Supernovae obtained from the full Sloan Digital Sky Survey II Supernova Survey, supplemented with host-galaxy spectroscopy from the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey. Our photometric-classification method is based on the supernovae typing technique of Sako et al. (2011), aided by host galaxy redshifts (0:05 < z < 0:55). SuperNova ANAlysis simulations of our methodology estimate that we have a Type Ia Supernovae typing efficiency of 70.8%, with only 3.9% contamination from Core-Collapse Supernovae. We demonstrate that this level of contamination has no effect on our cosmological constraints. We quantify and correct for our selection effects (e.g., Malmquist bias) using simulations. When fitting to a flat Λ Cold Dark Matter cosmological model, we find that our photometric sample alone gives Ωm = 0:24+0.07-0.05 (statistical errors only). If we relax the constraint on flatness, then our sample provides competitive joint statistical constraints on Ωm and Ωλ, comparable to those derived from the spectroscopically-confirmed three-year Supernova Legacy Survey. Using only our data, the statistics–only result favors an accelerating Universe at 99.96% confidence. Assuming a constant w Cold Dark Matter cosmological model, and combining with H0, Cosmic Microwave Background and Luminous Red Galaxies data, we obtain w = -0:96+0.10-0.10, Ωm = 0.29+0.02-0.02 and Ωk = 0.00+0.01-0.01 (statistical errors only), which is competitive with similar spectroscopically-confirmed Type Ia Supernovae analyses. Overall this comparison is reassuring, considering the lower redshift leverage of the Sloan Digital Sky Survey II Supernova Survey sample (z < 0:55) and the lack of spectroscopic confirmation used herein. These results demonstrate the potential of photometrically-classified Type Ia Supernovae samples in improving cosmological constraints, as well as promoting additional investigations of Type Ia Supernovae host galaxy correlation and possible Type Ia Supernovae lensing. We briefly discuss these issues in this thesis.