CCD Observations of Clusters of Galaxies.

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Abstract

A sample of 84 Abell clusters has been investigated to determined photometric properties of brightest clusters (G1's) as a function of cluster richness. Seventy-five new measurements of cluster redshifts are presented. Direct imaging of the core of each cluster was affected using CCD detectors. The dispersion in the luminosity of G1's within an aperture of 16 kpc radius is only 0.34 mag. The richness correction is 0.10 mag per Abell richness class. There has been no color evolution in giant ellipticals since redshifts of 0.25. The surface brightness profiles of G1's are represented fairly well by either a de Vaucouleurs model (mean effective radius is 28 kpc) or a modified Hubble law (mean core radius is 2.1 kpc). These scale lengths are three and five times the values for second- and third-ranked galaxies, respectively. The average aperture correction factor ((alpha)) for G1's is 0.7. Luminosity functions for the cores of 60 of these clusters have been analyzed. The G1's cannot be drawn from a universal luminosity function. Excluding G1 from the luminosity function results in satisfactory Schechter function fits to the rest of the cluster members. The power-law slope at low luminosities is (TURN) -1, and the observed dispersion in M(,*) as a function of richness matches that predicted from numerical simulations. The evidence for dynamical evolution is very strong. Nearly half of the G1's are multiple systems. A detailed study of a brightest cluster galaxy composed of nine nuclei is presented, which indicates mergers can radically alter a galaxy in only a billion years. The strong (alpha)-luminosity relation for G1's allows removal of merger induced effects.
Original languageEnglish (US)
JournalThesis (PH.D.)--CALIFORNIA INSTITUTE OF TECHNOLOGY, 1982.Source: Dissertation Abstracts International
StatePublished - Mar 1 1982
Externally publishedYes

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