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   PR # 43044
   The masses and profiles (for both the visible and dark components) in
   galaxy clusters, as well as their dynamical state, are key
   cosmological issues. X-Ray bright clusters where gravitational
   lensing occurs are favoured laboratories for such studies: X-ray
   observations provide total mass estimates through the hydrostatic
   equation whereas lensing data are mass estimators, independant of the
   dynamical state. We propose to perform a 50 ksec ASCA observation of
   the lensing cluster A521 to obtain the essential temperature
   information. The ASCA data will be combined with ROSAT/HRI imagery
   data, optical (photometry and multi-object spectroscopy) data and
   lensing data to study the consistency between the various mass
   estimates and to probe the galaxies and ICM dynamical states.
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