Dark Energy Constraints from the Cosmic Age and Supernova

Abstract

Using the low limit of cosmic ages from globular cluster and the white dwarfs: $t_0 > 12$Gyr, together with recent new high redshift supernova observations from the HST/GOODS program and previous supernova data, we give a considerable estimation of the equation of state for dark energy, with uniform priors as weak as $0.2<Ω_m<0.4$ or $0.1<Ω_m h^2<0.16$. We find cosmic age limit plays a significant role in lowering the upper bound on the variation amplitude of dark energy equation of state. We propose in this paper a new scenario of dark energy dubbed Quintom, which gives rise to the equation of state larger than -1 in the past and less than -1 today, satisfying current observations. In addition we've also considered the implications of recent X-ray gas mass fraction data on dark energy, which favors a negative running of the equation of state.

Figures (6)

• Figure 1: Age and SNe Ia constraints on $\Lambda$CDM cosmology. Left panel: The red area is excluded by $t_0>12$Gyr and the blue area is excluded by the assumption for $t_0<20$Gyr for $\Lambda$CDM model. The area between the two solid lines is allowed by $1\sigma$ HST limit. Right panel: $2\sigma$ SNe Ia limit on $\Lambda$CDM model. The dashed line corresponds to the $1\sigma$ limit and the dot inside denotes the best fit value. The navy area is allowed by age constraint 12Gyr $<$$t_0$$<$ 20 Gyr.
• Figure 2: Right panel: $2\sigma$ SNe Ia limit alone on Model A dark energy. Left panel: $2\sigma$ SNe Ia limit and age limit ($t_0>12$Gyr) on Model A dark energy. The dots inside the two panels show the best fit parameters.
• Figure 3: Age and SNe limits on Model A with different priors as noted inside. The dots inside the 1$\sigma$ dashed lines denote the best fit parameters.
• Figure 4: The same as Fig.3 for Model B.
• Figure 5: The evolution of the effective equation of state of the double scalar fields given in Eq. (\ref{['double']}). The parameters are chosen as: $V_0=8.38\times 10^{-126}m_p^4$, $\lambda=20$. We set the initial conditions as: $\phi_{1i}=-1.7 m_p$, $\phi_{2i}=-0.2292 m_p$, which lead to $\Omega_{m0}=0.30$, $w_{{\rm eff} 0}=-2.44$.