Spectroscopic confirmation of the Cl 1604 supercluster at z ∼ 0.9

We present spectroscopic confirmation of the Cl 1604 supercluster at z similar to 0.9. The supercluster was originally detected as two individual clusters, Cl 1604 + 4304 at z = 0.90 and Cl 1604 + 4321 at z = 0.92, which are closely separated in both redshift and sky position. Subsequent imaging revealed a complex of red galaxies bridging the two clusters, suggesting that the region contained a large-scale structure. We have carried out extensive multiobject spectroscopy, which, combined with previous measurements, provides similar to600 redshifts in this area, including 230 confirmed supercluster members. We detect two additional clusters that are part of this structure, Cl 1604 + 4314 at z = 0.87 and Cl 1604 + 4316 at z = 0.94. All four have properties typical of local clusters, with line-of-sight velocity dispersions between 489 and 962 km s(-1). The structure is significantly extended in redshift space, which, if interpreted as a true elongation in real space, implies a depth of. We examine the spatial and redshift distribution of the supercluster members.