090178

Superclusters as the largest cosmic structures are important to study the evolution of galaxy clusters and groups cosmic baryons (e.g. the warm hot intergalactic medium) and galaxy evolution. There have been few studies of superclusters in X-rays while the X-ray data remain as the key to study the bulk of baryons in superclusters. We select the two richest superclusters from the SDSS/redMaPPer cluster catalog and propose XMM observations to map both of them. They are extreme mass concentrations with the total mass at least several times higher than well-known superclusters like A901/2. The XMM data will be used to map the mass distribution (along with our weak-lensing work) study merger dynamics and examine the cosmic filaments and provide us important insights on superclusters. [truncated! Please see actual data for full text]