The Angular Clustering of Distant Galaxy Clusters
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We discuss the angular clustering of galaxy clusters at z > 1 selected within 50 deg2 from the Spitzer Wide-Infrared Extragalactic survey. We use a simple color selection to identify high-redshift galaxies with no dependence on galaxy rest-frame optical colorusing Spitzer IRAC 3.6 and4.5 μm photometry. The majority (>90%) of galaxies with z > 1.3 are identified with ([3.6] - [4.5])AB > -0.1 mag. We identify candidate galaxy clusters at z > 1 by selecting overden-sities of ≥26-28 objects with [3.6] - [4.5] > -0.1 mag within radii of 1.4′, which corresponds to r < 0.5 h-1 Mpc at z = 1.5. These candidate galaxy clusters show strong angular clustering, with an angular correlation function represented by w(θ) = (3.1 ± 0.5)(θ/1′)-.1±0.1 over scales of 2′-100′. Assuming the redshift distribution of these galaxy clusters follows a fiducial model, these galaxy clusters have a spatial-clustering scale length r0 = 22.4 ± 3.6 h-1 Mpc and a comoving number density n = 1.2 ± 0.1 × 10-5 h2 Mpc-3. The correlation scale length and number density of these objects are comparable to those of rich galaxy clusters at low redshift. The number density of these high-redshift clusters corresponds to dark matter halos larger than (3-5) × 1013 h-1 M ⊙ at z = 1.5. Assuming the dark halos hosting these high-redshift clusters grow following ACDM models, these clusters will reside in halos larger than (1-2) × 1014 h-1 M ⊙ at z = 0.2, comparable to rich galaxy clusters. © 2008. The American Astronomical Society. All rights reserved.
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