The impact of gas physics on strong cluster lensing

¹ Zentrum für Astronomie der Universität Heidelberg, ITA, Albert-Überle-Str. 2, 69120 Heidelberg, Germany e-mail: puchwein@ita.uni-heidelberg.de
² Dipartimento di Astronomia, Università di Padova, Vicolo dell'Osservatorio 2, 35120 Padova, Italy
³ Max-Planck-Institut für Astrophysik, PO Box 1523, 85740 Garching, Germany

Received: 8 April 2005
Accepted: 10 May 2005

Abstract

Previous studies of strong gravitational lensing by galaxy clusters have neglected the potential impact of the intracluster gas. Here, we compare simulations of strong cluster lensing including gas physics at increasing levels of complexity, i.e. with adiabatic, cooling, star-forming, feedback-receiving, and thermally conducting gas, along with different implementations of the artificial viscosity in the SPH simulations. Each cluster was simulated starting from the same initial conditions so as to allow direct comparison of the simulated clusters.
We compare the clusters' shapes, dynamics, and density profiles and then study their strong-lensing cross sections computed by means of ray-tracing simulations. With the common viscosity implementation, adiabatic gas has little effect on strong cluster lensing, while lower viscosity allows stronger turbulence, thus higher non-thermal pressure and a generally broader gas distribution, which tends to lower lensing cross sections. Conversely, cooling and star formation steepen the core density profiles and can thus increase the strong-lensing efficiency considerably.