http://arxiv.org/abs/1311.1254
A spatial clustering signal has been established in Spitzer/IRAC measurements of the unresolved Cosmic near-Infrared Background (CIB) out to large angular scales, ~1 deg. This CIB signal, while significantly exceeding the contribution from the remaining known galaxies, was further found to be coherent at a statistically significant level with the unresolved soft Cosmic X-ray Background (CXB). This measurement probes the unresolved CXB to very faint source levels using deep near-IR source subtraction. We study contributions from extragalactic populations at low to intermediate redshifts to the measured positive cross-power signal of the CIB fluctuations with the CXB. We model the X-ray emission from AGN, normal galaxies and hot gas, calculating their CXB contribution including spatial coherence with all infrared emitting counterparts. We construct a new population model of the HMXB/LMXB dominated galaxies and reproduce source counts from the deepest Chandra surveys. We use a halo model framework to calculate the auto and cross-power spectra of the unresolved fluctuations based on the latest constraints of the halo occupation distribution of AGN, galaxies and diffuse emission. We find that the combined contribution from these populations is unable to produce the CIB vs CXB cross-power needed to explain the data, particularly at large angular scales. At 4.5mic vs 0.5-2 keV, the large scale cross-power is (4.2+-1.6)% of the best-fit model to the data, rising to (42+-10)% towards small angular scales. The discrepancy suggests that the signal originates from the same population producing the CIB clustering signal out to ~1 deg.
Thu, 7 Nov 13
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