Supernovae constraints on models of dark energy reexamined

We use the Type Ia Supernova gold sample data of Riess et al in order to constrain three models of dark energy. We study the Cardassian model, the Dvali-Turner gravity modified model, and the generalized Chaplygin gas model of dark energy–dark matter unification. In our best-fit analysis for these three dark energy proposals we consider the flat model and the nonflat model priors. We also discuss the degeneracy of the models with the XCDM model through the computation of the so-called jerk parameter.

Figure 1

Confidence contours in the ${\Omega }_m-n$ parameter space for the flat Cardassian model. The solid and dashed lines represent the 68% and 95% confidence regions, respectively; in the left panel are shown the results for the gold sample without the HST SNe Ia, whereas in the right panel, the full gold sample is taken into account.

Figure 2

Confidence contours in the ${\Omega }_m-n$, ${\Omega }_k-{\Omega }_m$, and ${\Omega }_k-n$ parameter space for the nonflat Cardassian model. As in Fig. 1, the solid and dashed lines represent the 68% and 95% confidence regions, respectively; in the left panel the golden sample is used without HST SNe Ia, whereas in the right one the full gold sample is taken into account.

Figure 3

Confidence contours in the ${\Omega }_m-\beta$ parameter space for the flat DT model. The solid and dashed lines represent the 68% and 95% confidence regions, respectively; in the left panel are shown the results for the gold sample without the HST SNe Ia, whereas in the right the full gold sample is taken into account.

Figure 4

Confidence contours in the ${\Omega }_m-\beta$ and ${\Omega }_k-{\Omega }_m$ parameter space for the nonflat DT model using the gold sample without HST SNe Ia (left panel) and in the ${\Omega }_m-\beta$ and ${\Omega }_k-\beta$ plane using the full gold sample (right panel). As in Fig. 3, the solid and dashed lines represent the 68% and 95% confidence regions, respectively.

Figure 5

Confidence contours in the and $A_s-\alpha$, parameter space for the flat GCG model. The solid and dashed lines represent the 68% and 95% confidence regions, respectively.

Figure 6

Confidence contours in the ${\Omega }_k-A_s$ and ${\Omega }_k-\alpha$ parameter space for the nonflat GCG model. The solid and dashed lines represent the 68% and 95% confidence regions, respectively.