Redshift‐Space Distortions and the Real‐Space Clustering of Different Galaxy Types

Abstract

We study the distortions induced by peculiar velocities on the redshift-space correlation function of galaxies of di erent morphological types in the Pisces-Perseus redshift survey. Redshift-space distortions a ect early-and late-type galaxies in di erent ways. In particular, at small separations the dominant e ect comes from virialized cluster cores, where ellipticals are the dominant population. The net result is that a meaningful comparison of the clustering strength of di erent morphological types can be performed only in real space, i.e., after projecting out the redshift distortions on the two-point correlation function n). A power-law t to the projected function on scales smaller than 10 h~1 Mpc m(r p , w p (r p ) gives h~1 Mpc, for the early-type population, and h~1 Mpc, r 0 \ 8.35 ~0.76 `0.75 c \ 2.05 ~0.08 `0.10 r 0 \ 5.55 ~0.45 `0.40 for spirals and irregulars. These values are derived for a sample luminosity limited to c \ 1.73 ~0.08 `0.07 We detect a 25% increase of with luminosity for all types combined, from M Zw [19.5. r 0 M Zw \ [19 to [20. In the framework of a simple stable clustering model for the mean streaming of pairs, we estimate the one-dimensional pairwise velocity dispersion between 0 and 1 h~1 Mpc, to be p 12 (1), 865 ~165 `250 km s~1 for early-type galaxies and km s~1 for late types. This latter value should be a fair esti-345 ~65