The Pisces-Perseus supercluster and gravitational quasi-equilibrium clustering

We analyze the three-dimensional spatial-velocity distribution of the count s-in-cells for 4501 galaxies in the Pisces-Perseus supercluster. This is do ne for the total sample, for a subset containing the most conspicuous galax ies (brightest members with large intrinsic linear diameters), and for a su bset containing the least conspicuous galaxies (faintest members with small intrinsic linear diameters). We also examine subsets limited by absolute m agnitudes as well as volume limited samples. The counts-in-cells distributi on functions for all these samples are described remarkably well by the gra vitational quasiequilibrium distribution which was previously found to fit the more statistically homogeneous Zwicky, CfA, ESO, and IRAS catalogs. For the complete Pisces-Perseus sample, the value of b, representing the ratio of gravitational correlation energy to the kinetic energy of peculiar moti ons is 0.8. The most conspicuous galaxies are somewhat more uniformly distr ibuted than the least conspicuous ones which tend to follow the overall dis tribution. A dendrogram analysis shows that groups of the most conspicuous galaxies tend to be located near groups of the least conspicuous ones. We also analyze the velocity distribution in different parts of the supercl uster. There is a dense core of about 750 galaxies which have an overall Ga ussian velocity distribution with a dispersion of about 450 km s(-1) around the mean of 5260 km s(-1). However this region is not completely relaxed s ince it contains subgroups which may not have Gaussian distributions. Moreo ver, in most subgroups the crossing time exceeds the Hubble time, indicatin g incomplete relaxation. Irregular galaxies tend to concentrate in this reg ion, perhaps indicating significant tidal interactions. Spatial distribution functions measured for increasing numbers of galaxies around the dense core of Pisces-Perseus approach the form and have the valu e of b observed in larger statistically homogeneous catalogs. It appears th at greater than or similar to 10(3) galaxies in this region constitute a "f air sample" with a wide range of structures characteristic of gravitational clustering. Our results appear consistent with the supercluster forming gravitationally as an accumulation of smaller clusters. Accurate peculiar velocities of th ese galaxies would help decide whether this clustering was stimulated by a larger scale perturbation or occurred by chance.