2008ApJ...676..206P

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 color using Spitzer IRAC 3.6 and 4.5 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 overdensities 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 wθ=3.1±0.5θ/1'^–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±0.1x10^–5 h³/Mpc3. 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 3-5x10¹³ h^–1 M_☉ at z=1.5. Assuming the dark halos hosting these high-redshift clusters grow following ΛCDM models, these clusters will reside in halos larger than 1-2x10¹⁴ h^–1 M_☉ at z=0.2, comparable to rich galaxy clusters.