Observational Constraints on a Variable Dark Energy Model
  We study the effect of a phenomenological parameterized quintessence model on low, intermediate and high redshift observations. At low and intermediate redshifts, we use the Gold sample of supernova Type Ia (SNIa) data and recently observed size of baryonic acoustic peak from Sloan Digital Sky Survey (SDSS), to put constraint on the parameters of the quintessence model. At the high redshift, the same fitting procedure is done using WAMP data, comparing the location of acoustic peak with that obtain from the dark energy model. As a complementary analysis in a flat universe, we combine the results from the SNIa, CMB and SDSS. The best fit values for the model parameters are $\Omega_m = 0.27^{+0.02}_{-0.02}$ (the present matter content) and $w_0=-1.45^{+0.35}_{-0.60}$ (dark energy equation of state). Finally we calculate the age of universe in this model and compare it with the age of old stars and high redshift objects 
M. Sadegh Movahed, Sohrab Rahvar