The SPLASH and Chandra COSMOS Legacy Survey: the Cross Power Between Near-Infrared and X-Ray Background Fluctuations
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Date
2018-09-10
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Citation of Original Publication
Li, Yanxia et al. The SPLASH and Chandra COSMOS Legacy Survey: The Cross-power between Near-infrared and X-Ray Background Fluctuations. The Astrophysical Journal 864 (Sept. 10, 2018), no. 141.
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Abstract
We study the source-subtracted near-infrared and X-ray background fluctuations of the COSMOS field using data from
the Spitzer SPLASH program (∼1272 hours) and Chandra COSMOS Legacy Survey (4.6 Ms). The new auto power spectra
of the cosmic infrared and X-ray background fluctuations reach maximum angular scales of ∼ 300000 and ∼ 500000, respectively.
We measure the cross power spectra between each infrared and X-ray band and calculate the mean power above 2000. We find that
the soft X-ray band is correlated with 3.6 and 4.5µm at ∼ 4 σ significance level. The significance between hard X-ray and the
3.6µm (4.5µm) band is ∼ 2.2 σ (∼ 3.8 σ). The combined infrared (3.6 + 4.5µm) data are correlated with the X-ray data in soft
([0.5-2] keV), hard ([2-7] keV) and broad ([0.5-7] keV) bands at ∼ 5.6 σ, ∼ 4.4 σ and ∼ 6.6 σ level, respectively. We compare
the new measurements with existing models for the contributions from known populations at z<7, which are not subtracted. The
model predictions are consistent with the measurements but we cannot rule out contributions from other components, such as
Direct Collapse Black Holes (DCBH). However, the stacked cross-power spectra, combining other available data, show excess
fluctuations about an order of magnitude on average at ∼4σ confidence at scales within ∼30000. By studying the X-ray SED of
the cross-power signal, assuming no significant variation from the infrared, we find that its shape is consistent with DCBHs.