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

[106.12] Keck II Spectroscopy of Ten New Distant Clusters of Galaxies Associated with Bent Double Radio Sources from the FIRST Survey

E. L. Blanton, D. J. Helfand (Columbia U.), R. H. Becker (U.C. Davis), M. D. Gregg (IGPP/LLNL), R. L. White (STScI)

Bent double and triple radio sources attain their morphologies as the result of the relative motion between their host galaxies and the intracluster media in which they are embedded. Thus, they make good tracers of the high density Universe and are detectable to high redshifts. We present Keck II LRIS multi-slit mask spectroscopy of ten fields surrounding bent radio sources selected from the VLA FIRST (Faint Images of the Radio Sky at Twenty-cm) survey (Becker, White, amp; Helfand 1995). Clusters or groups with concordant redshifts are found in all of the fields, with 0.32 < z < 0.85, confirming that this is a powerful new technique for locating distant clusters of galaxies. In addition, we present near-infrared images of fields that were blank to R \approx 22-23 at the position of the radio source, but that reveal overdensities of galaxies in the K-band suggesting that these may be clusters at even higher redshifts. The FIRST project is supported by grants from the National Geographic Society, the National Science Foundation, NATO, IGPP, Columbia University, and Sun Microsystems.

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