Double source lensing probing high redshift cosmology

Abstract

Double source lensing, with two sources lensed by the sameforeground galaxy, involves the distance between each sourceand the lens and hence is a probe of the universe away fromthe observer. The double source distance ratio also reduces sensitivity tothe lens model and has good complementarity with standarddistance probes. We show that using this technique at highredshifts z > 1, to be enabled by data from the Euclid satellite and other surveys, can give insights on dark energy, both in terms of w 0–w a and redshift binned density. We find a dark energy figure of merit of 245 from combination of 256 double source systems with moderate quality cosmic microwave background and supernova data. Using instead five redshift bins between z = 1.1–5, we could detect the dark energy density out to z ≈ 5, or make measurements ranging between 31σ and 2.5σ of its values in the bins.