Redshift Survey of 12 Moderate-redshift Clusters

We conducted a redshift survey of 12 X-ray selected clusters in the redshift range z = 0.35–0.50 with MMT/Hectospec. The redshift surveys confirm that these clusters are massive systems. There are no massive groups or clusters projected along the line of sight that might contaminate the observed cluster X-ray properties significantly. We identify 25–79 members per cluster and refine the estimates of each cluster’s mean redshift. We include the 8004 new redshifts in Data Behind the Figure.