1996/06/25 by Petra Stein, P. Stein, Stein, P.
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics (astro-ph) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Scientific Research and Discoveries #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9606162
Accepted for publication in A&A. 7 pages in LaTeX, including 2 Postscript figures
arxiv created 1996/06/25 · openalex publication_date 1996/06/25 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
A homogeneous sample of galaxy redshifts in the core regions (R < 0.5 h-1 Mpc) of 12 clusters is used to measure the frequency of substructure with different tests. In 50 % of the cases substructure is detected, a frequency which agrees well with previous studies of cluster cores. Magnitude information and rough morphological classes are also available for 80 % of the sample, allowing us to confirm that bright galaxies (M < -22 mag) have a significantly lower velocity dispersion than the rest. Elliptical galaxies are the main responsibles for this luminosity segregation in velocity space, whereas no segregation can be seen for spiral galaxies. Given the coincidence of substructure and luminosity segregation, a cluster model with an old population of ellipticals which are under the effect of dynamical friction in each subcluster is thus favoured by these observations. Spiral galaxies seem to be late arrivals, or are passing in front or behind the core of the cluster.