Cosmological constraints from COMBO-17 using 3D weak lensing

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 deg(2) in total, providing a conditional constraint in the (sigma(8), Omega(m)) plane as well as a conditional constraint on the equation of state of dark energy, parametrizedby a constant w p(de)/rho(dc)c(2). The (sigma(8), Omega(m)) plane analysis constrained the relation between sigma(8) and Omega(m) to be sigma(8)(Omega(m)/0.3)(0.57 +/- 0.19) = 1.06(-0.16)(+0.17), 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(-0.70)(+0.64). 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(-0.58)(+0.61). 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.