In my past life, I was an astrophysicist at the University of Kansas. I worked on the dynamics and evolution of galaxy clusters, concentrating on the analysis of optical and X-ray observations.
My Astrophysics Publications
Quantification of Optical Substructure
Here's a summary of substructure tests for all rich clusters with at least 50 measured redshifts (for data obtained and reduced before August 1995). Galaxies lie within 1.5 Mpc (H0 = 100) and within 3-sigma of the mean velocity.
Correlations between Optical and X-ray Properties of Clusters
Here are the kinematical and dynamical properties of clusters of galaxies (some irregular, primarily cD-type) with and without correction for substructure. See Bird, 1994, AJ, 107, 1637 for more details. Bold-face cluster names give properties without substructure correction; names of subclusters (substructure-corrected) all end in the letters ``splt''. I'd take the estimated masses with a large grain of salt! This work is summarized in Bird, Mushotzky & Metzler, 1995 ApJ.
Effects of Substructure on galaxy cluster mass determinations
If I'd stuck with astrophysics as a career, I would probably have been working on -- or been funded by -- the Chandra X-Ray Observatory. Observations of Abell cluster A2142 reveal dramatic contrasts in the cluster's X-ray emission, indicative of smaller groups of galaxies, merging together to form the richer, denser cluster itself. My thesis work concluded that most clusters are young objects, objects in which evidence of the building blocks (the groups of galaxies) are still evident. This work from A2142 allows astronomers to observe the individual groups directly, without lots of perverse statistical contortions. Way to go, NASA.
Here's the paper the team working on A2142 published.