Time-varying dark energy constraints from the latest SN Ia, BAO and SGL

Qing-Jun Zhang, Yue-Liang Wu
2010 Journal of Cosmology and Astroparticle Physics  
Based on the latest SNe Ia data provided by Hicken et al. (2009) with using MLCS17 light curve fitter, together with the Baryon Acoustic Oscillation(BAO) and strong gravitational lenses(SGL), we investigate the constraints on the dark energy equation-of-state parameter w in the flat universe, especially for the time-varying case w(z)=w_0+w_zz/(1+z). The constraints from SNe data alone are found to be: (a) (Ω_M, w)=(0.358, -1.09) as the best-fit results; (b) (w_0, w_z)=(-0.73^+0.23_-0.97,
more » ... .66_-10.34) for the two parameters in the time-varying case after marginalizing the parameter Ω_M; (c) the likelihood of parameter w_z has a high non-Gaussian distribution; (d) an extra restriction on Ω_M is necessary to improve the constraint of the SNe Ia data on the parameters (w_0, w_z). A joint analysis of SNe Ia data and BAO is made to break the degeneracy between w and Ω_M, and leads to the interesting maximum likelihoods w_0 = -0.94 and w_z = 0. When marginalizing the parameter Ω_M, the fitting results are found to be (w_0, w_z)=(-0.95^+0.45_-0.18, 0.41^+0.79_-0.96). After adding the splitting angle statistic of SGL data, a consistent constraint is obtained (Ω_M, w)=(0.298, -0.907) and the constraints on time-varying dark energy are further improved to be (w_0, w_z) = (-0.92^+0.14_-0.10, 0.35^+0.47_-0.54), which indicates that the phantom type models are disfavored.
doi:10.1088/1475-7516/2010/08/038 fatcat:7j3yqtgcsfcwbof7unaqy4i7dy