The Cl2236-04 lens cluster: looking for a third gravitational image?

Abstract

We present deep imaging and spectroscopy of three blue objects in the Cl2236-04 cluster-lens which follow-up the discovery of a bright arc in the center of the cluster (Melnick et al., 1993), and the model of the matter distribution of this lens (Kneib et al., 1993). The redshift measured for the predicted counter-image of the arc is found to be z = 1.334 instead of z = 1.116 observed for the arc. This proves that these are not multiple images of the same source. A new model is presented. The source of the arc is reconstructed and shows a bimodal shape, resembling two merging galaxies. This explains the velocity gradient seen in the arc and allows us to predict the redshifts of some of the arclets detected in the cluster.