Constraining the dark energy equation of state with double source plane strong lenses

TL;DR

This paper explores using double source plane strong gravitational lenses to constrain dark energy's equation of state, offering a method that is independent of the Hubble parameter and complements existing cosmological probes.

Contribution

It demonstrates that a small number of double source plane systems can provide competitive constraints on dark energy parameters, and highlights the method's orthogonal degeneracy to CMB and BAO data.

Findings

Constraints comparable to current data with few systems

Method's degeneracy is orthogonal to CMB and BAO

Potential for high-precision dark energy measurements

Abstract

We investigate the possibility of constraining the dark energy equation of state by measuring the ratio of Einstein radii in a strong gravitational lens system with two source planes. This quantity is independent of the Hubble parameter and directly measures the growth of angular diameter distances as a function of redshift. We investigate the prospects for a single double source plane system and for a forecast population of systems discovered by re-observing a population of single source lenses already known from a photometrically selected catalogue such as CASSOWARY or from a spectroscopically selected catalogue such as SLACS. We find that constraints comparable to current data-sets (15% uncertainty on the dark equation of state at 68%CL) are possible with a handful of double source plane systems. We also find that the method's degeneracy between Omega_M and w is almost orthogonal to that of CMB and BAO measurements, making this method highly complimentary to current probes.