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

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 H_0=69+-6(stat.)+-4(syst.) km s^{-1}Mpc^{-1}. In combination with WMAP9, the constraints on dark energy are Omega_w=0.68+-0.05 and w=-0.86+-0.17 in a flat model with constant equation-of-state.Comment: 6 pages; accepted for publication on MNRA

The Hubble constant inferred from 18 time-delay lenses

We present a simultaneous analysis of 18 galaxy lenses with time delay measurements. For each lens we derive mass maps using pixelated simultaneous modeling with shared Hubble constant. We estimate the Hubble constant to be 66_{-4}^{+6} km/s/Mpc (for a flat Universe with \Omega_m=0.3, \Omega_\Lambda=0.7). We have also selected a subsample of five relatively isolated early type galaxies and by simultaneous modeling with an additional constraint on isothermality of their mass profiles we get H_0=76 +/-3 km/s/Mpc.Comment: 11 page, 4 figures, Accepted for publication in Ap

Gravitational lenses as cosmic rules:omega(m), omega(lambda) from time delays and velocity dispersions

We show that a cosmic standard ruler can be constructed from the joint measurement of the time delay, $\Delta \tau$, between gravitationally lensed quasar images and the velocity dispersion, σ, of the lensing galaxy. This is specifically shown, for a singular isothermal sphere lens, $D_{\rm OL} \propto \Delta \tau / \sigma^2$, where DOL is the angular diameter distance to the lens. Using MCMC simulations we illustrate the constraints set in the $\Omega_{\rm m}-\Omega_{\Lambda}$ plane from future observations