Recent CHANDRA and XMM observations of two very different galaxy   clusters: RBS797 and CL 0939+4713
  RBS797 and CL 0939+4713 are two intermediate red-shift clusters ($z=0.35-0.41$). They have very different morphologies but both show surprisingly interesting structures. RBS797 looks relaxed, with an almost circular morphology; a CHANDRA observation of this cluster has revealed two deep depressions in the X-ray emission near the core. CL 0939+4713 has instead an irregular morphology with evident substructures which seem to be in the process of merging. 
E. De Filippis, S. Schindler and A. Castillo-Morales