The impact of AGN feedback and baryonic cooling on galaxy clusters as gravitational lenses

We investigate the impact of active galactic nucleus (AGN) feedback on the gravitational lensing properties of a sample of galaxy clusters with masses in the range 1014-1015 M-circle dot, using state-of-the-art simulations. Adopting a ray-tracing algorithm, we compute the cross-section of giant arcs from clusters simulated with dark matter (DM) only physics, DM plus gas with cooling and star formation (CSF) and DM plus gas with cooling, star formation and AGN feedback (CSFBH). Once AGN feedback is included, baryonic physics boosts the strong-lensing cross-section by much less than previously estimated using clusters simulated with only CSF. For a cluster with a virial mass of 7.4 x 1014 M-circle dot, inclusion of baryonic physics without feedback can boost the cross-section by as much as a factor of 3, in agreement with previous studies, whereas once AGN feedback is included this maximal figure falls to a factor of 2 at most. Typically, clusters simulated with DM and CSFBH physics have similar cross-sections for the production of giant arcs. We also investigate how baryonic physics affects the weak-lensing properties of the simulated clusters by fitting NFW profiles to synthetic weak-lensing data sets using a Markov Chain Monte Carlo approach, and by performing non-parametric mass reconstructions. Without the inclusion of AGN feedback, measured concentration parameters can be much larger than those obtained with AGN feedback, which are similar to the DM-only case.