A High-Significance Measurement of Correlation Between Unresolved IRAS Sources and Optically-Selected Galaxy Clusters

TL;DR

This study measures a highly significant correlation between unresolved infrared sources and galaxy clusters, revealing insights into the clustering of faint cosmic infrared background sources and their relation to galaxy clusters.

Contribution

It presents the first high-significance measurement of the correlation between IRAS unresolved sources and galaxy clusters, constraining cluster bias and demonstrating the method's potential for future surveys.

Findings

Cross-power spectrum detected at over 40 sigma significance.

Cluster bias constrained to 2.6 +/- 1.4, consistent with previous studies.

Power-law index of the cross-spectrum is -1.28 +/- 0.12.

Abstract

We cross-correlate the 100 um Improved Reprocessing of the IRAS Survey (IRIS) map and galaxy clusters at 0.1 < z < 0.3 in the maxBCG catalogue taken from the Sloan Digital Sky Survey, measuring an angular cross-power spectrum over multipole moments 150 < l < 3000 at a total significance of over 40 sigma. The cross-spectrum, which arises from the spatial correlation between unresolved dusty galaxies that make up the cosmic infrared background (CIB) in the IRIS map and the galaxy clusters, is well-fit by a single power law with an index of -1.28 +/- 0.12, similar to the clustering of unresolved galaxies from cross-correlating far-infrared and submillimetre maps at longer wavelengths. Using a recent, phenomenological model for the spectral and clustering properties of the IRIS galaxies, we constrain the large-scale bias of the maxBCG clusters to be 2.6 +/- 1.4, consistent with existing analyses of the real-space cluster correlation function. The success of our method suggests that future CIB-optical cross-correlations using Planck and Herschel data will significantly improve our understanding of the clustering and redshift distribution of the faint CIB sources.