Constraining the equation of state of the Universe from distant Type Ia supernovae and cosmic microwave background anisotropies
Abstract
We analyse the constraints that can be placed on a cosmological constant or quintessence-like component by combining observations of Type Ia supernovae with measurements of anisotropies in the cosmic microwave background. We use the recent supernovae sample of Perlmutter et al and observations of the CMB anisotropies to constraint the equation of state (w_Q = p/rho) in quintessence-like models via a likelihood analysis. The 2 sigma upper limits are w_Q < -0.6 if the Universe is assumed to be spatially flat, and w_Q < -0.4 for universes of arbitrary spatial curvature. The upper limit derived for a spatially flat Universe is close to the lower limit (w_Q approx -0.7) allowed for simple potentials, implying that additional fine tuning may be required to construct a viable quintessence model.