Hubble constant and dark energy inferred from free-form determined time delay distances

Abstract

Time delays between multiple images of lensed sources can probe the geometry of the universe. We propose a novel method based on free-form modelling of gravitational lenses to estimate time delay distances and, in turn, cosmological parameters. This approach does not suffer from the degeneracy between the steepness of the profile and the cosmological parameters. We apply the method to 18 systems having time delay measurements and find H0= 69 ± 6(stat.) ± 4(syst.) km s-1Mpc-1. In combination with Wilkinson Microwave Anisotropy Probe 9, the constraints on dark energy are ωw = 0.68 ± 0.05 and w =-0.86 ± 0.17 in a flat model with constant equation of state. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Published by Oxford University Press on behalf of the Royal Astronomical Society.