Michael S. Vogeley

The CfA Redshift Survey: Data for the South Galactic Cap*

We present redshifts for a sample of 4391 galaxies with magnitude mB(0) ≤ 15.5 covering 20h ≤ α ≤ 4h in right ascension and -25 ≤ δ ≤ 90° in declination. This sample is complete for all galaxies in the merge of the Zwicky et al. and Nilson catalogs in the south Galactic cap. Redshifts for 2964 of these were measured as part of the second CfA Redshift Survey. The data reveal large voids in the foreground and background of the Perseus-Pisces Supercluster. The largest of these voids lies at a mean velocity ~8000 km s-1, has diameter ~5000 km s-1, and is enclosed by a complex of dense structures. The large structure known as the Perseus-Pisces Supercluster forms the near side of this complex. On the far side of this large void, at a mean velocity ~12,000 km s-1, there is another coherent dense wall. The structures in this survey support the view that galaxies generally lie on surfaces surrounding or nearly surrounding low-density regions or voids.

The kinematics of dense clusters of galaxies. I. The data

We have measured redshifts in the fields of the 31 R greater than 1 Abell clusters with z of 0.02-0.05 and absolute b exp II above 30 deg. At least ten of the fields are severely contaminated by superimposed velocity peaks. We derive the mean velocities and velocity dispersions of the 25 dense peaks in the sample. The abundance of peaks, 6.6 x 10 exp -6 h-cubed Mpc exp -3, is consistent with the mean number density of R above 1 Abell clusters. The range of velocity dispersions is 304-1346 km/s. The median dispersion is 718 km/s. The subset of eight systems with cD galaxies has a median velocity dispersion of 792 km/s, close to that of non-cD systems (626 km/s). When these data are combined with 16 cD cluster velocity dispersions from our previous study (Zabludoff et al., 1990, or ZHG) and Dunn (1991), eight of 25 cD galaxies have peculiar motions larger than half the cluster velocity dispersions. These findings further support the conclusions of Beers and Geller (1983), ZHG, and Dunn (1991), who argue that cD galaxies do not lie in the global kinematic center, but in local potential minima. If so, systems with speeding cDs are probably a guide to substructure in dynamically evolving systems.