Tracking quintessence by cosmic shear - Constraints from VIRMOS-Descart and CFHTLS and future prospects

Context. Dark energy can be investigated in two complementary ways, by considering either general parameterizations or physically well-defined models. This article follows the second route a nd explores the observational constraints on quintessence models where the acceleration of our universe is driven by a slow-rolling sca lar field. The analysis focuses on cosmic shear, combined wit h type Ia supernovae data and cosmic microwave background observations. Aims. This article examines how weak lensing surveys can constrain dark energy, how they complement supernovae data to lift some degeneracies and addresses some issues regarding the limitations due to the lack of knowledge concerning the non-linear regime. Methods. Using a Boltzmann code that includes quintessence models and the computation of weak lensing observables, we determine the shear power spectrum and several two-point statistics. The non-linear regime is described by two different mappings. The likelihood analysis is based on a grid method. The data include the “gold set” of supernovae Ia, the WMAP-1 year data and the VIRMOS-Descart and CFHTLS-deep and -wide data for weak lensing. This is the first analysis of h igh-energy motivated dark energy models that uses weak lensing data. We explore larger angular scales, using a synthetic realization of the complete CFHTLS-wide survey as well as next space-based missions surveys. Results. Two classes of cosmological parameters are discussed: i) those accounting for quintessence affect mainly geometrical factors; ii) cosmological parameters specifying the primordial universe strongly depend on the description of the non-linear regime. This dependence is addressed using wide surveys, by discarding the smaller angular scales to reduce the dependence on the non-linear regime. Special care is payed to the comparison of these physical models with parameterizations of the equation of state. For a flat universe and a quintessence inverse power law potential with slopeα, we obtainα < 1 and Q0 = 0.75 +0.03 −0.04 at 95% confidence level, whereas α = 2 +18 −2 , Q0 = 0.74 +0.03 −0.05 when including supergravity corrections.