Journal
ASTROPHYSICAL JOURNAL
Volume 556, Issue 2, Pages L75-L78Publisher
IOP PUBLISHING LTD
DOI: 10.1086/322991
Keywords
galaxies : Seyfert; X-rays : diffuse background; X-rays : galaxies
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We present a composite 1-10 keV Seyfert 2 X-ray spectrum derived from ASCA observations of a distance-limited sample of nearby galaxies. All 29 observed objects were detected. Above similar to3 keV, the composite spectrum is inverted, confirming that Seyfert 2 galaxies as a class have the spectral properties necessary to explain the flat shape of the cosmic X-ray background spectrum. Integrating the composite spectrum over redshift, we find that the total emission from Seyfert 2 galaxies, combined with the expected contribution from unabsorbed type I objects, provides an excellent match to the spectrum and intensity of the hard X-ray background. The principal uncertainty in this procedure is the cosmic evolution of the Seyfert 2 X-ray luminosity function. Separate composite spectra for objects in our sample with and without polarized broad optical emission lines are also presented.
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