A Composite Seyfert 2 X-Ray Spectrum: Implications for the Origin of the Cosmic X-Ray Background
Abstract
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 ~3 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 1 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2001
- DOI:
- 10.1086/322991
- arXiv:
- arXiv:astro-ph/0106519
- Bibcode:
- 2001ApJ...556L..75M
- Keywords:
-
- Galaxies: Seyfert;
- X-Rays: Diffuse Background;
- X-Rays: Galaxies;
- Astrophysics
- E-Print:
- 11 pages (AASTeX), including 3 figures. Accepted for publication in ApJ Letters