Cluster-Cluster Strong Lensing: Expectations and Detection Methods
  We calculate the all-sky number of galaxy clusters that are expected to be gravitationally lensed by foreground massive clusters. We describe the redshift and number distributions of clusters using a Press-Schechter analysis, and model the foreground lensing clusters as singular isothermal spheres. If Omega_m=0.3 and Omega_Lambda=0.7, we expect ~ 30 cluster-cluster strong lensing events that involve foreground X-ray luminous clusters with total mass greater than 7.5 x 10^14 h^-1 M_sun, or X-ray luminosity L_x (2-10 keV) 8 x 10^44 h^-2 ergs s^-1, and background clusters with total mass greater than 10^14 h^-1 M_sun. The number expected in an open universe with Omega_m = 0.3 is less than \~ 4. Because of uncertainty in sigma_8, the root-mean-square density fluctuations in spheres of radius 8 h^-1 Mpc, the exact number of such lensing events is uncertain by a factor of about 5. We examine methods to detect cluster-cluster lensing events based on optical, X-ray, and Sunyaev-Zel'dovich effect observations. 
Asantha R. Cooray, Gilbert P. Holder, Jean M. Quashnock (University of   Chicago)