REDSHIFT-SPACE DISTORTIONS AND THE REAL-SPACE CLUSTERING OF DIFFERENTGALAXY TYPES

We study the distortions induced by peculiar velocities on the redshif t-space correlation function of galaxies of different morphological ty pes 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 differen t morphological types can be performed only in real space, i.e., after projecting out the redshift distortions on the two-point correlation function xi(r(p), pi). A power-law fit to the projected function w(p)( r(p)) on scales smaller than 10 h(-1) Mpc gives r(0) = 8.35(-0.76)(+0. 75) h(-1) Mpc, gamma = 2.05(-0.08)(+0.10) for the early-type populatio n, and r(0) = 5.55(-0.45)(+0.40) h(-1) Mpc, gamma = 1.73(-0.08)(+0.07) for sprials and irregulars. These values are derived for a sample lum inosity limited to M-Zw less than or equal to -19.5. We detect a 25% i ncrease of r(0) with luminosity for all types combined, from M-Zw = -1 9 to -20. In the framework of a simple stable clustering model for the mean streaming of pairs, we estimate sigma(12)(1), the one-dimensiona l pairwise velocity dispersion between 0 and 1 h(-1) Mpc, to be 865(-1 65)(+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 pai rwise dispersion for ''field'' galaxies; it is stable with respect to the presence or absence of clusters in the sample, and is consistent w ith the values found for noncluster galaxies and IRAS galaxies at simi lar separations.