AAS Meeting #193 - Austin, Texas, January 1999
Session 38. Galaxy Clusters
Display, Thursday, January 7, 1999, 9:20am-6:30pm, Exhibits Hall 1

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[38.17] A Spectroscopic Survey of the Palomar Distant Cluster Catalog.

B. P. Holden (Univ. of Chicago), R. C. Nichol (Carnegie Mellon Univ.), C. Adami (Northwestern Univ.), F. J. Castander (Univ. of Chicago), L. M. Lubin (Cal. Inst. of Technology), A. Mazure (IGRAP Laboratoire d'Astronomie Spatiale), M. P. Postman (STScI), A. K. Romer (Carnegie Mellon Univ.), M. P. Ulmer (Northwestern Univ.)

We have conducted a redshift survey of seventeen candidates from the optically selected Palomar Distant Cluster Survey (PDCS; Postman et. al. 1996). Our goals are to determine both the space density of the PDCS and the accuracy of the redshift estimates from the PDCS cluster finding algorithm. If we constrain our sample to clusters with an estimated redshift less then 0.5, we measure a scatter in redshift of 0.08 with respect to the estimated redshifts for eleven cluster candidates. Of these eleven, six have three or more redshifts in agreement. Using this subsample of six clusters, we estimate the space density of Richness Class 1 and 2 clusters in the PDCS. Our results are quite consistent with the original space density estimates of the PDCS, and agree with the results of Bahcall et. al. 1997. We are continuing our survey using extensive multi-object spectroscopy with the goal of measuring 50 redshifts per cluster to determine velocity dispersions, velocity profiles and eliminate false positive detections from the PDCS. As the PDCS is a uniform, statistical sample that was constructed from a computer-based algorithm, we can estimate the space density of objects as a function velocity dispersion and mass. Such measurements will allow us to constrain structure formation parameters such as normalization of the power spectrum on cluster scales. These results demonstrate the power of such optical cluster catalogs and are only a taste the results to come from future surveys with similar techniques.


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