Evidence for the missing baryons in the angular correlation of the diffuse X-ray background

M. Galeazzi, A. Gupta, E. Ursino

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


The amount of detected baryons in the local universe is at least a factor of 2 smaller than that measured at high redshift. It is believed that a significant fraction of the baryons in the current universe is "hiding" in a hot filamentary structure filling the intergalactic space, the warm-hot intergalactic medium (WHIM). We found evidence of the missing baryons in the WHIM by detecting their signature on the angular correlation of diffuse X-ray emission with the XMM-Newton satellite. Our result indicates that 12%± 5% of the total diffuse X-ray emission in the energy range 0.4-0.6 keV is due to intergalactic filaments. The statistical significance of our detection is several sigmas (χ2 > 136, N = 19). The error bar in the X-ray flux is dominated, instead, by cosmic variation and model uncertainties.

Original languageEnglish (US)
Pages (from-to)1127-1131
Number of pages5
JournalAstrophysical Journal
Issue number2
StatePublished - Apr 20 2009


  • Large-scale structure of universe
  • X-rays: diffuse background

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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