Are the Einstein Radii of Galaxy Clusters Consistent with LCDM
The discrepancy between the observed and predicted strong lensing properties of galaxy clusters present a source of tension for LCDM cosmology. However, more complete treatment of baryonic processes in simulations and self-consistent cluster selection may reduce this tension.
In this talk, I use the X-ray selected $z>0.5$ MACS cluster sample, as a case in point, and present the relationship between Einstein radii, X-ray luminosities and inferred masses, comparing those found for the high-z MACS sample with predictions at $z=0.5$ and $z=0.6$ from LCDM hydrodynamic simulations that include --- along with other baryonic processes --- star formation, chemical evolution, supernovae and AGN feedback. Along the way, I discuss the importance of selection criteria (X-¬ray flux, mass and/or dynamical state), the large (mock) sample¬-to-¬sample variation due to cluster triaxiality, and mass modelling.