AAS 207th Meeting, 8-12 January 2006
Session 112 Going Shallow, Going Deep: Clusters
Poster, Wednesday, 9:20am-6:30pm, January 11, 2006, Exhibit Hall

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[112.05] Clusters of Galaxies in the First Half of the Universe from the IRAC Shallow Survey

P.R. Eisenhardt, M. Brodwin (JPL/Caltech), A.H. Gonzalez (U. Florida), S.A. Stanford (UC Davis), D. Stern (JPL/Caltech), M. Brown (Princeton U.), A. Dey, B.T. Jannuzi (NOAO), S. Perlmutter, K. Dawson (LBL)

The number of known galaxy clusters at z > 1 remains small, largely because such objects are challenging to detect using only optical data. Due to their greatly enhanced rate of star formation by z ~1, the UV emission from modest sized field galaxies overwhelms the intrinsically red spectra of quiesecent, early type galaxies preferentially found in clusters. The contrast of high redshift clusters over the field improves at longer wavelengths, but the contrast against atmospheric emission declines, making surveying sufficient z > 1 volume a formidable undertaking. With the launch of the Spitzer Space Telescope in 2003, sensitive infrared arrays free from foreground thermal emission were put into operation. The Spitzer Infrared Array Camera (IRAC) shallow survey covers 8.5 square deg2, using 90 second exposures per position, but is nevertheless sensitive enough to discover galaxy clusters well beyond z = 1. Spectroscopic confirmation of IRAC shallow survey selected clusters at z = 1.11, 1.24, 1.37, and 1.41 is presented in a separate talk by Brodwin et al. Here we present the methodology of the IRAC shallow survey cluster search, along with some statistical properties of the clusters. Seven of the clusters are the targets of an HST cycle 14 ACS imaging program to search for z > 1 SNe in ellipticals, and we present some initial results from these high resolution cluster images.

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