Galaxy Cluster Correlation Function to z ~ 1.5 in the IRAC Shallow Cluster Survey

TL;DR

This study measures the clustering of galaxy clusters up to redshift 1.5, showing strong, persistent clustering consistent with massive halo structures, and compares observations with cosmological simulations.

Contribution

First measurement of galaxy cluster autocorrelation function up to z ~ 1.5 in the IRAC Shallow Cluster Survey, confirming strong clustering of massive clusters at high redshift.

Findings

Strong clustering observed at z=0.5 with r_0 ≈ 17.4 h^-1 Mpc.

Clustering persists at z=1 with r_0 ≈ 19.1 h^-1 Mpc.

Clusters are consistent with halo masses around 10^{14} Msun.

Abstract

We present the galaxy cluster autocorrelation function of 277 galaxy cluster candidates with 0.25 \le z \le 1.5 in a 7 deg^2 area of the IRAC Shallow Cluster Survey. We find strong clustering throughout our galaxy cluster sample, as expected for these massive structures. Specifically, at <z> = 0.5 we find a correlation length of r_0 = 17.40^{+3.98}_{-3.10} h^-1 Mpc, in excellent agreement with the Las Campanas Distant Cluster Survey, the only other non-local measurement. At higher redshift, <z> = 1, we find that strong clustering persists, with a correlation length of r_0=19.14^{+5.65}_{-4.56} h^-1 Mpc. A comparison with high resolution cosmological simulations indicates these are clusters with halo masses of \sim 10^{14} Msun, a result supported by estimates of dynamical mass for a subset of the sample. In a stable clustering picture, these clusters will evolve into massive (10^{15} Msun) clusters by the present day.