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Session 106 - Clusters of Galaxies.
Display session, Saturday, January 10
Exhibit Hall,

[106.02] The DPOSS Cluster Survey

R. R. Gal, S. G. Djorgovski, S. C. Odewahn (Caltech), R. R. de Carvalho (Observatorio Nacional, Brasil)

There are many cosmological uses for rich clusters of galaxies. They provide useful constraints for theories of large-scale structure formation and evolution, and are valuable (possibly coeval) samples for studying galaxy evolution in dense environments. Studies of the cluster two-point correlation function and the power spectrum are important probes of large scale structure and the scenarios of its formation.

In view of the real need to generate well-defined, objective catalogs of galaxy clusters and groups, with well-understood selection criteria and completeness, we use DPOSS to create just such a catalog. The DPOSS has two main advantages over previous surveys: it goes a magnitude fainter than POSS-I, and allows us to use color information in selecting our candidates. The digitization and cataloging of objects allow us to detect clusters in an objective manner, unlike many previous surveys. Here we report on the preliminary results of this effort.

We utilize the (g-r)vs.(r-i) color-color diagram to select for early-type galaxies, which are more likely to be cluster members. We then use the adaptive kernel method to generate galaxy surface density maps, from which cluster candidates are selected. We not only successfully recover Abell clusters of richness class 0 and higher but also find many new cluster candidates which were apparently missed by Abell. In one DPOSS field, we find an average of 50 cluster candidates, or \sim1.5/sq. deg. These clusters are expected to span the redshift range 0This work is supported in part by a grant from the Norris Foundation.

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