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 deg2 in total, providing a conditional constraint in the (σ8, Ωm) plane as well as a conditional constraint on the equation of state of dark energy, parametrized by a constant w≡pde/ρdec2. The (σ8, Ωm) plane analysis constrained the relation between σ8 and Ωm to be σ8(Ωm/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.