Lensing Time Delays and Cosmological Complementarity

TL;DR

Time delays in strong gravitational lensing, combined with supernova and CMB data, significantly enhance constraints on dark energy, matter density, and Hubble constant, especially with detailed lens modeling and monitoring.

Contribution

This paper quantifies the cosmological parameter constraints achievable by combining time delay lensing data with supernova and CMB observations, highlighting the potential improvements.

Findings

Dark energy figure of merit improved by nearly 5 times

Matter density  0.004 precision

Hubble constant h determined to 0.7%

Abstract

Time delays in strong gravitational lensing systems possess significant complementarity with distance measurements to determine the dark energy equation of state, as well as the matter density and Hubble constant. Time delays are most useful when observations permit detailed lens modeling and variability studies, requiring high resolution imaging, long time monitoring, and rapid cadence. We quantify the constraints possible between a sample of 150 such time delay lenses and a near term supernova program, such as might become available from an Antarctic telescope such as KDUST and the Dark Energy Survey. Adding time delay data to supernovae plus cosmic microwave background information can improve the dark energy figure of merit by almost a factor 5 and determine the matter density \Omega_m to 0.004, Hubble constant h to 0.7%, and dark energy equation of state time variation w_a to 0.26, systematics permitting.