Clustering of the IR Background Light withSpitzer: Contribution from Resolved Sources

Abstract

We describe the angular power spectrum of resolved sources at 3.6 μm (L band) in Spitzer imaging data of the GOODS HDF-N, the GOODS CDF-S, and the NDWFS Bootes field in several source magnitude bins. We also measure angular power spectra of resolved sources in the Bootes field at Ks and J bands using ground-based IR imaging data. In the three bands, J, Ks, and L, we detect the clustering of galaxies on top of the shot-noise power spectrum at multipoles between l ~ 102 and 105. The angular power spectra range from the large, linear scales to small, nonlinear scales of galaxy clustering, and in some magnitude ranges show departure from a power-law clustering spectrum. We consider a halo model to describe clustering measurements and to establish the halo occupation number parameters of IR bright galaxies at redshifts around one. The typical halo mass scale at which two or more IR galaxies with L-band Vega magnitude between 17 and 19 are found in the same halo is between 9 × 1011 and 7 × 1012 M☉ at the 1 σ confidence level; this is consistent with the previous halo mass estimates for bright, red galaxies at z ~ 1. We also extend our clustering results and completeness-corrected faint-source number counts in GOODS fields to understand the underlying nature of unresolved sources responsible for IR background (IRB) anisotropies that were detected in deep Spitzer images. While these unresolved fluctuations were measured at subarcminute angular scales, if a high-redshift diffuse component associated with first galaxies exists in the IRB, then it's clustering properties are best studied with shallow, wide-field images that allow a measurement of the clustering spectrum from a few degrees to arcminute angular scales.