Astronomy

Cosmic Correlation

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Science  14 Jun 2013:
Vol. 340, Issue 6138, pp. 1267
DOI: 10.1126/science.340.6138.1267-a
CREDIT: NICO CAPPELLUTI

The cosmic infrared background, the integrated infrared light produced by all extragalactic sources in the universe, has been found to exceed the expected emissions from known galaxies, including the most distant ones. To understand the nature of the populations responsible for this excess, Cappelluti et al. cross-correlated the fluctuations in the infrared and x-ray backgrounds. The infrared background is sensitive to stellar populations, whereas the x-ray background probes radiation from accreting black holes and thermal x-ray emission from hot ionized gas. The detected correlations indicate that at least 15 to 20% of the cosmic infrared background is produced by sources that are powerful x-ray emitters. Based on theoretical calculations, Yue et al. propose in a different study that the first cosmic black holes, which formed from direct collapse of the gas in the first galaxy halos, are responsible for the infrared background fluctuations. This hypothesis is consistent with the observed correlation between the infrared and x-ray backgrounds.

Astrophys. J. 769, 68; (2013) Mon. Not. R. Astron. Soc. 10.1093/mnras/stt826 (2013).

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