Exploring the Virialization Region of the Massive Merging Cluster Abell 401

We propose mosaic observations of the massive, earlystage, binary mergingcluster Abell 401 to probe the ICM out to the virial radius with essentiallyfull azimuthal coverage. Simulations of structure formation predict relativelylarge numbers of cool gas clumps in such systems, with more clumps expectedalong filaments. Abell 401/Abell 399 is a perfect example of such a system, withthe only intercluster filament detected by Planck. We will apply the XCOPmethod of combining Xray and SZ observations to accurately determine thethermodynamic profiles of the ICM, with and without clump filtering, tomeasure the clumping factor and fraction of nonthermal pressure support bothalong and away from the putative cosmic filament and compare the results with expectations from simulations. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]