IMAGING OF 16 DISTANT EMSS CLUSTERS WITH Z-GREATER-THAN-OR-EQUAL-TO-0.2 AND LX.44-GREATER-THAN-OR-EQUAL-TO-4 - NEW ARCS AND 1ST CONSEQUENCES

Medium-deep V, R, and I observations of a subsample of 16 clusters of galaxies in the EMSS sample defined from the Einstein satellite data are presented. Three new cases of clusters with giant luminous arcs (length/width > 10, V < 22) have been discovered together with six new arcs (4 < l/w < 10, V < 22), and we propose that these arcs are new examples of gravitational lensing of background galaxies by the rich clusters. Combined with giant luminous arcs already observed in the EMSS sample, there is a total of six giant luminous arcs observed in the sample of 16 clusters. This high rate of success in finding arcs added to their axis ratio distribution is consistent with very small core radii (< 100 kpc) for the dark matter distribution in rich clusters, and rules out models in which dark matter follows the X-ray gas.