Dark energy with gravitational lens time delays

Understand

Strong lensing gravitational time delays are a powerful and cost effective probe of dark energy.

• Recent studies have shown that a single lens can provide a distance measurement with 6-7 % accuracy (including random and systematic uncertainties), provided sufficient data are available to determine the time delay and reconstruct the gravitational potential of the deflector.
• Gravitational-time delays are a low redshift (z~0-2) probe and thus allow one to break degeneracies in the interpretation of data from higher-redshift probes like the cosmic microwave background in terms of the dark energy equation of state.
• Current studies are limited by the size of the sample of known lensed quasars, but this situation is about to change.