We present spectroscopic confirmation of the Cl 1604 supercluster at z \sim 0.9 .
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 multi-object spectroscopy , which , combined with previous measurements , provides \sim 600 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 93 ~ { } h _ { 70 } ^ { -1 } ~ { } { Mpc } .
We examine the spatial and redshift distribution of the supercluster members .