We discuss the angular clustering of galaxy clusters at z > 1 selected within 50 deg ^ { 2 } from the Spitzer Wide-Infrared Extragalactic survey .
We employ 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 ( \hbox { $ [ 3.6 ] $ } - \hbox { $ [ 4.5 ] $ } ) _ { \mathrm { AB } } > -0.1 mag .
We identify candidate galaxy clusters at z > 1 by selecting overdensities of \geq 26–28 objects with \hbox { $ [ 3.6 ] $ } - \hbox { $ [ 4.5 ] $ } > -0.1 mag within radii of 1.4 arcminutes , 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 ( \theta ) = ( 3.1 \pm 0.5 ) ( \theta / 1 \arcmin ) ^ { -1.1 \pm 0.1 } over scales of 2–100 arcminutes .
Assuming the redshift distribution of these galaxy clusters follows a fiducial model , these galaxy clusters have a spatial–clustering scale length r _ { 0 } = 22.4 \pm 3.6 h ^ { -1 } Mpc , and a comoving number density n = 1.2 \pm 0.1 \times 10 ^ { -6 } h ^ { 3 } 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 correspond to dark–matter halos larger than 3 - 5 \times 10 ^ { 13 } h ^ { -1 } \mathcal { M } _ { \odot } at z = 1.5 .
Assuming the dark halos hosting these high–redshift clusters grow following \Lambda CDM models , these clusters will reside in halos larger than 1 - 2 \times 10 ^ { 14 } h ^ { -1 } \mathcal { M } _ { \odot } at z = 0.2 , comparable to rich galaxy clusters .