Exploring the properties of dark energy using type-Ia supernovae and other datasets

We reconstruct dark energy properties from two complementary supernova datasets - the newly released Gold + HST sample and SNLS. The results obtained are consistent with the standard Lambda CDM model within 2 sigma error bars, although the Gold + HST data favour evolving dark energy slightly more than SNLS. Using complementary data from baryon acoustic oscillations and the cosmic microwave background to constrain dark energy, we find that our results in this case are strongly dependent on the present value of the matter density Omega(0m). Consequently, no firm conclusions regarding constancy or variability of dark energy density can be drawn from these data alone unless the value of Omega(0m) is known to an accuracy of a few per cent. However, possible variability is significantly restricted if these data are used in conjunction with supernova data.