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Resolving the extragalactic hard X-ray background

Author

Listed:
  • R. F. Mushotzky

    (NASA Goddard Space Flight Center)

  • L. L. Cowie

    (Institute for Astronomy, University of Hawaii)

  • A. J. Barger

    (Institute for Astronomy, University of Hawaii)

  • K. A. Arnaud

    (NASA Goddard Space Flight Center
    University of Maryland)

Abstract

The origin of the hard (2–10 keV) X-ray background has been a mystery for over 35 years. Most of the soft X-ray background has been resolved into individual sources (mainly quasars), but these sources do not have the spectral energy distribution required to match the spectrum of the X-ray background as a whole. Here we report the results of a deep survey, using the Chandra satellite, in which the detected hard X-ray sources account for at least 75 per cent of the hard X-ray background. The mean X-ray spectral energy distribution of these sources is in good agreement with that of the background. Moreover, most of those hard X-ray sources are associated unambiguously with either the nuclei of otherwise normal bright galaxies, or with optically faint sources. The latter could be active nuclei in dust-enshrouded galaxies or a population of quasars at extremely high redshift.

Suggested Citation

  • R. F. Mushotzky & L. L. Cowie & A. J. Barger & K. A. Arnaud, 2000. "Resolving the extragalactic hard X-ray background," Nature, Nature, vol. 404(6777), pages 459-464, March.
    • Handle: RePEc:nat:nature:v:404:y:2000:i:6777:d:10.1038_35006564
    DOI: 10.1038/35006564
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