DETAILED LENSING PROPERTIES OF THE MS-2137-2353 CORE AND RECONSTRUCTION OF SOURCES FROM HUBBLE-SPACE-TELESCOPE IMAGERY

A deep HST image of the core of the cluster of galaxies MS 2137-2353 h as revealed detailed morphological structures in two are systems, whic h are modeled and well reproduced. An analysis of the lensing properti es of the dark matter component indicates that the cluster could have a mass distribution almost as simple as a single elliptical mass distr ibution, with ellipticity and angular orientation similar to those in visible and X-ray light. This suggests that MS 2137-2353 is a relaxed cluster at z = 0.313. The predicted density profile (rho similar to r( -1.75+/-0.09), with r(c) less than or equal to 17 h(50)(-1) kpc) withi n 150 h(50)(-1) kpc, implies a M/L ratio increasing with the radius, a nd could be in agreement with predictions from standard CDM simulation s. Two faint sources (unlensed magnitude R = 23.5 and 25.6) at the sam e redshift are aligned with the cluster core and are responsible for t he are systems. They have been reconstructed with details as small as 0.'' 015 (or 120 h(50)(-1) pc in the source assumed at z = 1), and sho w complex morphology, which for one source could be related to a close interacting pair and/or to dust. They also show strong signs of star formation, indicated by compact H II regions away from their centers. Because magnification factors of the giant luminous are are large, our method can even resolve the size of a giant H II region at z similar to 1.