Galaxy Groups: Morphological Segregation Between Spirals

Extract

We have considered the sample of groups of galaxies identified by M. J. Geller and J. P. Huchra (1983, Astrophys. J. Suppl. 52, 61), omitting the groups which are part of well-known clusters or those which are probably affected by the presence of interlopers. We have searched for possible morphological segregation among spirals in galaxy groups considering the mean-pairwise distance of the members of the galaxy system and the mean distance of the members from the center of the system. All the distances are normalized to the mean-pairwise distance (MPD) and to the mean distance from the center (CD), respectively, of all the members of the groups considered. We divided the family of the spirals (plus irregulars) into two subfamilies (S′ and S″); we included in S′ the early-type spirals (with morphological type code 0≤T≤2) and in S″ the galaxies of the late morphological types (with T ≥ 3). The median values of the ratios MPD(S′)/MPD, MPD(S″)/MPD, CD(S′)/CD, CD(S″)/CD are 0.86, 1.17, 0.95, 1.08, respectively.