2007MNRAS.376..771K

We present the first application of the 3D cosmic shear method developed in Heavens, Kitching & Taylor and the geometric shear-ratio analysis developed in Taylor et al., to the COMBO-17 data set. 3D cosmic shear has been used to analyse galaxies with redshift estimates from two random COMBO-17 fields covering 0.52 deg² in total, providing a conditional constraint in the (σ₈, Ω_m) plane as well as a conditional constraint on the equation of state of dark energy, parametrized by a constant w ≡ p_de/ρ_dec². The (σ₈, Ω_m) plane analysis constrained the relation between σ₈ and Ω_mto be σ₈(Ω_m/0.3)^0.57±0.19 = 1.06^+0.17_–0.16, in agreement with a 2D cosmic shear analysis of COMBO-17. The 3D cosmic shear conditional constraint on w using the two random fields is w = -1.27^+0.64_–0.70. The geometric shear-ratio analysis has been applied to the A901/2 field, which contains three small galaxy clusters. Combining the analysis from the A901/2 field, using the geometric shear-ratio analysis, and the two random fields, using 3D cosmic shear, w is conditionally constrained to w = -1.08^+0.63_–0.58. The errors presented in this paper are shown to agree with Fisher matrix predictions made in Heavens, Kitching & Taylor and Taylor et al. When these methods are applied to large data sets, as expected soon from surveys such as Pan-STARRS and VST-KIDS, the dark energy equation of state could be constrained to an unprecedented degree of accuracy.