Linear clusters of galaxies
Linear clusters may impose constraints on cluster evolution and formation models. New data and analytical methods are presented. Three clusters (A194, A999 and A1016) that have been classified as linear by Rood and Sastry (1971) are studied. Using galaxy positions and redshifts, the author assigns cluster membership. He devises a measure of linearity and obtains a value for each cluster and for 120 spherically symmetric models. He estimates that A999 can probably be represented by a spherically symmetric distribution, but A1016 and A194 are probably linear. He estimates that {approx lt}8% of a catalog of spherically symmetric clusters, if classified by eye, might be erroneously categorized as linear. Statistical methods used to search for galaxy alignments are reassessed and a non-parametric tests is proposed. No evidence was found for alignment in the convincingly linear systems (A194 and A1016). All three clusters were tested for luminosity segregation and for variations in the velocity or surface distributions of galaxies as a function of morphological type. The elliptical cluster members of A194 tend to be more luminous (by {approximately} 0.3 magnitudes) than either the spiral or SO galaxies; no other evidence of segregation was found.
- Research Organization:
- Harvard Univ., Boston, MA (USA)
- OSTI ID:
- 5179572
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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