GRAVITATIONAL LENSING PAIRS IN CLUSTERS OF GALAXIES - A NEW PROBE TO THE HIGH-REDSHIFT UNIVERSE

The possibility of a new class of gravitationally lensed objects in cl usters of galaxies is discussed: faint pairs of highly magnified image s, which are on the. same side of the cluster and close together. We c alculate that there could be several such pairs in every lensing clust er if the number counts of faint galaxies continued to rise up to B = 29-30, with the same slope as for brighter sources, reaching values of order 1000 arcmin-2. Such faint sources should also have small angula r sizes, approximately 0.''1, in order for the two magnified images to remain separate, rather than merging into an arc. It is argued that s uch an abundance of faint sources would not be surprising in the conte xt of the CDM model, where a large number of low circular velocity hal os, which could host dwarf galaxies, are present at high redshift. The discovery and observation of a large number of such magnified pairs o f images would provide unprecedented information on galaxy evolution a nd galaxy populations at high redshift.