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J.G. Nollenberg, L.L.R. Williams (University of Minnesota)
We report results from a new technique for determining the degree of reddening and extinction due to nearby, z<0.08, medium rich galaxy clusters. This technique involves selecting "Cluster" and "Control" areas on plates; Cluster areas are circular and are centered on galaxy clusters taken from the APM Galaxy Cluster Catalog, while Control areas are concentric annuli that surround the Cluster areas, and contain relatively unextincted galaxies. Cluster and Control areas are dominated by galaxies more distant than our nearby subset of APM clusters, thus dust effects nearly all of the Cluster area galaxies. On the color-magnitude (CM) plane, reddening and extinction by cluster dust shifts the distribution of Cluster area galaxies compared to the distribution of Control area galaxies by the "reddening vector". If a CM plane offset equal to minus the reddening vector is applied to the Cluster area galaxy distribution and subtracted from the Control area distribution, the residuals will be, in an ideal case, nil. Thus, to find the magnitude and direction of the reddening vector, we look for the CM offset that minimizes the residuals on the CM plane. Our analysis of 30 UKST plates yields preliminary results with upper limits on extinction of AR = 0.1 mag and reddenings of \Delta (B - V) = 0.08 mag, for cluster radii on the order of 1.1/h Mpc.
The author(s) of this abstract have provided an email address for comments about the abstract: manawa@astro.umn.edu