The Redshift-Distance Relation.VI. The Hubble Diagram from S20 Photometry for Rich Clusters and Sparse Groups: a Study of Residuals
Abstract
Magnitudes, corrected for aperture effect (to a standard metric diameter), for K dimming, and for galactic absorption are given in B, V, and R for 33 clusters, 20 RMS groups, and 45 galaxies associated with radio sources. The Rubble diagram for the first-ranked E or 50 galaxy in the smallest groups (population as sparse as five members) is the same as that for the great clusters to within 0.3 mag, which is 1 a of the distribution of absolute magnitude of the cluster galaxies themselves. The absolute magnitudes of first-ranked galaxies in compact groups, where the ratio of projected separation to angular diameter of the dominant galaxy is small (of order unity), are fainter, indicating some type of interaction between group members. A few clusters are abnormally bright in the Rubble diagram, and these are of Bautz-Morgan cluster types I and II. The magnitudes are not strongly correlated with richness, but the BautzMorgan effect is dominant and must be removed before a proper richness correlation can be made. absolute magnitude of first-ranked cluster galaxies is (Mv) = -23.30 + 0.38 (a) if H6 = 50 km s1 Mpc- . If the mean mass-to-light ratio is 30 visual solar units, the mean mass of such galaxies will be = 5 >c 1012 o + 40 percent. Subject headings: galaxies, clusters of - galaxies, photometry of
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 1973
- DOI:
- 10.1086/152262
- Bibcode:
- 1973ApJ...183..731S