A Proto-Supercluster Candidate Hosting a Massive Galaxy Cluster at z=1.75

We have discovered a large-scale structure candidate surrounding the massive, spectroscopically confirmed galaxy cluster IDCS J1426.5+3508 at z=1.75 in Boötes. Using a sample of mid-infrared-bright Dust-Obscured galaxies (DOGs) as signposts, we have identified 14 (39) galaxy cluster/group-scale overdense nodes of photo-z selected galaxies that are significant at >= 4 (3) sigma level at z=1.75. Our pipeline has also rediscovered the IDCS cluster with greater than 4 sigma significance. The filamentary proto-supercluster-like structure is spectroscopically confirmed, with ~ 30 AGN at 1.72 <= z_spec <= 1.78 from the AGES survey spanning its 50 Mpc x 35 Mpc extent. This is an unprecedented example of a massive (X-ray/SZ-detected) high redshift galaxy cluster still embedded in its birth environment. We report the initial characterization of this remarkable multi-nodal structure and establish the opportunities for future space and ground-based multiwavelength studies of the galaxy populations and ICM dynamics across the supercluster.