Probing the cross-power of unresolved cosmic infrared and X-ray backgrounds with upcoming space missions

Understand

The source-subtracted cosmic infrared background (CIB) fluctuations uncovered in deep Spitzer data cannot be explained by known galaxy populations and appear strongly coherent with unresolved cosmic X-ray background (CXB).

• This suggests that the source-subtracted CIB contains emissions from significantly abundant accreting black holes (BHs).
• We show that theoretically such populations would have the angular power spectrum which is largely independent of the epochs occupied by these sources, provided they are at z>~ 4, offering an important test of the origin of the new populations.
• Using the current measurements we reconstruct the underlying soft X-ray CXB from the new sources and show that its fluctuations, while consistent with a high-z origin, have an amplitude that cannot be reached in direct measurements with the foreseeable X-ray space missions.