Chandra and XMM-Newton Observations of the Most Extreme z > 1.25 ACTPol Survey C

SunyaevZel.dovich (SZ) surveys are currently the most powerful and consistentmethod of detecting high mass, high redshift galaxy clusters, whose dynamic,thermodynamic, and chemical properties serve as unique probes of the compositionand growth of structure in our Universe. The Atacama Cosmlogy Telescope (ACT)has surveyed >13000 sq. deg of sky, and the resulting ACTPol survey has detectedthousands of clusters (hundreds at z>1) based on their SZ signal. This proposaltargets the most massive highz ACTPol clusters without Xray followup,allowing us to obtain detailed measurements of cluster masses, morphologies, andthermodynamic properties, while nearly doubling the number of Xray observedclusters in this redshift range for which these measurement are possible. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]