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Session 54 - Large Scale Structure.
Display session, Tuesday, January 16
North Banquet Hall, Convention Center
We have been conducting a redshift survey of galaxy clusters to examine large scale structure in a 10^\circ \times 70^\circ strip of sky in the southern hemisphere using the new Meudon-ESO Fiber Optic Spectrograph (MEFOS) on the ESO 3.6m telescope. This strip was selected because it contains two particularly interesting supercluster candidates found by searching the Abell/ACO cluster catalog with a percolation algorithm (with previously measured and estimated redshifts for the clusters). Our sample is limited to richness class R\ge 1 clusters, with one or fewer measured redshifts, at high galactic latitude (the limits of Abell's statistical sample and \vert b\vert > 30^\circ for ACO clusters), with m_10 \le 19.0 (and estimated z < 0.20). One of our supercluster candidates is particularly interesting because it is in the largest high surface density region of the sky for Abell/ACO clusters with measured or estimated z < 0.20. There are 34 clusters in a roughly seven degree square in this part of Aquarius.
Our first run was in August 1994, and the data from those observations have been fully reduced, resulting in about 15 redshifts per cluster in 22 clusters in our strip. These redshifts reveal a pronounced overdensity of clusters at cz \sim 33000 km/sec. The approximate volume density of clusters is more than 10 times the average for R \ge 1 clusters. This overdensity is comparable to the Shapley Concentration and the Horologium and Corona Borealis superclusters. The presence of four such high-density supercluster structures within z < 0.12 puts a strong constraint on models of large scale strucuture.
Our second observing run occurred in September 1995. Twenty-six clusters were observed, resulting in an estimated 390 new redshifts.
