Close pairs of galaxies in rich clusters : A statistical analysis
Date
1994
Authors
Rutledge, Glen Alfred
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Abstract
The angular correlation function w(θ) is used to develop a statistically robust technique to search for an excess of close pairs of galaxies (linear projected separations less than 20 h⁻¹ kpc) superimposed on the overall density profile of rich clusters of galaxies. This technique is applied to 10 local (z < 0.1) rich clusters of galaxies. Abell 262 is found to have too few galaxies to be useful for this technique. Two clusters, Abell 400 and Abell 1904 are found to have at least a 2σ excess of close pairs, while Abell 1367, Abell 2670, and Hercules are found to have a 1σ excess. The remaining four clusters, Abell 401, Coma, Abell 2199, and Abell 2634 all show no significant excess of close pairs. The clusters that show an excess of close pairs tend to be of the dynamically less evolved Rood-Sastry (RS) types I, F, and C. The more dynamically evolved RS types B and cD do not show excesses. An exception to this trend is Abell 2670, which is a cD cluster that shows an excess of close pairs, and also appears to have substructure on the scale of 100 h⁻¹ kpc. This result is in agreement with the substructure studies of Bird (1994a, 1994b), which suggest that this cluster has recently undergone a line of sight merger.