Angular power spectra of optical and infrared background anisotropies at wavelengths between 0.5 and 5 μm are a useful probe of faint sources present during reionization, in addition to faint galaxies and diffuse signals at low redshift. The cross-correlation of these fluctuations with backgrounds at other wavelengths can be used to separate some of these signals. A previous study on the cross-correlation between X-ray and Spitzer fluctuations at 3.6 μm and 4.5 μm has been interpreted as evidence for direct collapse black holes present at z > 12. Here we return to this cross-correlation and study its wavelength dependence from 0.5 to 4.5 μm using Hubble and Spitzer data in combination with a subset of the 4 Ms Chandra observations in GOODS-S/ECDFS. Our study involves five Hubble bands at 0.6, 0.7, 0.85, 1.25, and 1.6 μm, and two Spitzer-IRAC bands at 3.6 μm and 4.5 μm. We confirm the previously seen cross-correlation between 3.6 μm (4.5 μm) and X-rays with 3.7σ (4.2σ) and 2.7σ (3.7σ) detections in the soft [0.5-2] keV and hard [2-8] keV X-ray bands, respectively, at angular scales above 20 arcsec. The cross-correlation of X-rays with Hubble is largely anticorrelated, ranging between the levels of 1.4σ-3.5σ for all the Hubble and X-ray bands. This lack of correlation in the shorter optical/NIR bands implies the sources responsible for the cosmic infrared background at 3.6 and 4.5 μm are at least partly dissimilar to those at 1.6 μm and shorter.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science