Quantification of Substructure in Nearby Abell Clusters

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Session 7 -- Clusters of Galaxies/Binary Galaxies
Display presentation, Monday, June 12, 1995, 9:20am - 6:30pm

[7.02] Quantification of Substructure in Nearby Abell Clusters

J.R. Kriessler, T.C. Beers (Michigan State), S.C. Odewahn (Minnesota)

Theory, as well as numerical simulations, suggests that $\Omega_o$ may be observationally constrained by the amount of substructure observed in present-day clusters of galaxies. We have therefore begun a study of the 116 Abell clusters with richness class greater than or equal to 1 and distance class less than or equal to 4, the so-called ``volume-limited'' sample of Hoessel, Gunn, \& Thuan 1980 (ApJ 241, 486) to determine the prevalence of substructure in the clusters' projected galaxy positions. We use positions of galaxies identified by the Minnesota Automated Plate Scanner to obtain contour plots of the available clusters using an adaptive kernel routine. Significance of substructure is evaluated using the 2-D Lee test as well as a likelihood-ratio test on fits made with mixtures of two-dimensional gaussians. We also present nonparametric density profile estimates obtained with the program MAPEL (Merritt and Tremblay 1994, AJ 108, 514).

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