Estimation of the cosmological parameters from an analysis of Type Ia supernovae with CMAGIC

This thesis presents a measurement of O m and O L from a blind analysis of 21 high redshift supernovae using a new technique (CMAGIC) for fitting the multi- color lightcurves of Type Ia supernovae, first introduced in Wang et al. (2003b). CMAGIC takes advantage of the remarkably simple behavior of Type Ia supernovae on color-magnitude diagrams, and has several advantages over previous techniques based on maximum magnitudes. Among these are a reduced sensitivity to host galaxy dust extinction, a shallower luminosity-width relation, and the relative simplicity of the fitting procedure. This technique can be used to cross check previous supernova cosmology results using currently existing data, despite the fact that these data sets were not observed in a manner optimized for CMAGIC. Because this analysis is being compared with a previous result, it is particularly important that the expectation of consistency does not introduce a bias into the analysis. To this end, a blind analysis has been performed, the first time that such a technique has been applied to the use of supernovae to measure the cosmological parameters.

Application of CMAGIC yields a measurement[Special characters omitted.] (statistical errors only), broadly confirming previous supernova measurements which indicated that the expansion of the Universe is accelerating. O m and O L are extremely correlated in this measurement, so the results are better stated in the principal axes frame of the resulting error ellipse:[Special characters omitted.] The systematic error has been estimated by considering alterations to the primary fit. The CMAGIC fit can also be directly compared with a fit using more traditional methods (the magnitude at B maximum, m B ) using the same set of supernovae. The CMAGIC results favor an accelerating Universe even more strongly than the m B results at the 1.6s level.