A theoretician's analysis of the supernova data and the limitations in determining the nature of dark energy II: Results for latest data

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  • 8 December 2003
Abstract
We extend our previous analysis of cosmological supernova Type Ia data (Padmanabhan & Choudhury 2003, MNRAS, 344, 823) to include the recent data points. A simple analysis, based on 194 data points, show that the main conclusions of our previous work remain unchanged. The full data set, as noted earlier, rules out decelerating models with high degree of significance. However, it is slightly worrying that the latest data also rules out the ``preferred'' flat model, which is supposed to be consistent with other observations, with a higher degree of significance than earlier. When the full data set is divided into two separate subsets consisting of low (z < 0.34) and high (z > 0.34) redshift supernova, it turns out that these two subsets, individually, admit decelerating models with zero dark energy. This is related to the fact that the best-fit value of the absolute magnitude of supernova Type Ia differ by about 0.5 magnitude for the two data subsets. We have also found that it is quite difficult to measure the evolution of the dark energy equation of state w_X(z) though its present value can be constrained quite well. The data seems to favour a dark energy component with current equation of state w_X < -1, thus opening the possibility of existence of more exotic forms of matter.

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