Redshift-space distortions and the real-space clustering of different galaxy types

We study the distortions induced by peculiar velocities on the redshift-space correlation function of galaxies of different morphological types in the Pisces-Perseus redshift survey. Redshift-space distortions affect early and late-type galaxies in different ways. In particular, at small separations the dominant effect comes from virialized cluster cores, where ellipticals are the dominant population. The net result is that a meaningful comparison of the clustering strength of different morphological types can be performed only in real space, i.e., after projecting out the redshift distortions on the two-point correlation function ξ(rp, π). A power-law fit to the projected function wp(rp) on scales smaller than 10 h-1 Mpc gives r0 = 8.35-0.76+0.75 h-1 Mpc, γ = 2.05-0.08+0.10 for the early-type population, and r0 = 5.55-0.45+0.40 h-1 Mpc, γ = 1.73-0.08+0.07 for spirals and irregulars. These values are derived for a sample luminosity limited to MZw ≤ -19.5. We detect a 25% increase of r0 with luminosity for all types combined, from MZw = -19 to -20. In the framework of a simple stable clustering model for the mean streaming of pairs, we estimate σ12(1), the one-dimensional pairwise velocity dispersion between 0 and 1 h-1 Mpc, to be 865-165+250 km s-1 for early-type galaxies and 345-65+95 km s-1 for late types. This latter value should be a fair estimate of the pairwise dispersion for "field" galaxies; it is stable with respect to the presence or absence of clusters in the sample, and is consistent with the values found for noncluster galaxies and IRAS galaxies at similar separations.