Cosmology with photometrically-classified type Ia Supernovae
Student thesis: Doctoral Thesis
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.
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