2012MNRAS.424.2864C

We investigate the possibility of constraining the dark energy equation of state by measuring the ratio of Einstein radii in a strong gravitational lens system with two source planes. This quantity is independent of the Hubble parameter and directly measures the growth of angular diameter distances as a function of redshift. We investigate the prospects for a single double-source plane system and for a forecast population of systems discovered by re-observing a population of single-source lenses already known from a photometrically selected catalogue such as Cambridge and Sloan survey of wide arcs in the sky or from a spectroscopically selected catalogue such as Sloan Lens ACS survey. We find that constraints comparable to current data sets (σ(w) ∼ 15 per cent) are possible with a handful of double-source plane systems. We also find that the method's degeneracy between Ω_M and w is almost orthogonal to that of cosmic microwave background and Baryon Acoustic Oscillations measurements, making this method highly complimentary to current probes. The large area KX quasar catalogue – I. Analysis of the photometric redshift selection and the complete quasar catalogue