Effects of early dark energy on strong cluster lensing

Zentrum für Astronomie, ITA, Universität Heidelberg, Albert-Überle-Str. 2, 69120 Heidelberg, Germany e-mail: cosimo@ita.uni-heidelberg.de

Received: 5 July 2006
Accepted: 5 September 2006

Abstract

We use the semi-analytic method developed earlier for computing strong-lensing optical depths to study the statistics of gravitational arcs in four dark-energy cosmologies. Specifically, we focus on models with early dark energy and compare them to more conventional models. Merger trees are constructed for the cluster population because strong cluster lensing is amplified by factors of two to three during mergers. We find that the optical depth for gravitational arcs in the early dark-energy models is increased by up to a factor of ~3 compared to the other models because of the modified dynamics of cluster formation. In particular, the probability of gravitational arcs in high-redshift clusters is considerably increased, which may offer an explanation for the unexpectedly high lensing efficiency of distant clusters.