AAS 200th meeting, Albuquerque, NM, June 2002
Session 17. AGN, QSOs and Active Galaxies
Oral, Monday, June 3, 2002, 10:00-11:30am, Ballroom A

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[17.04] ``Hidden'' Seyfert 2 Galaxies and the X-ray Background

E.C. Moran (Wesleyan U.), A.V. Filippenko (U.C. Berkeley)

Obscured active galactic nuclei, which are classified optically as type 2 (narrow-line) Seyfert galaxies, are the most promising candidates for the origin of the cosmic X-ray background radiation (XRB). However, optical follow-up observations of faint hard X-ray sources in deep Chandra images have revealed surprising numbers of apparently normal galaxies at modest redshift. This has prompted speculation that much of the XRB is produced by something other than Seyfert 2s. We contend that the faint Chandra sources are predominantly type 2 Seyferts whose nuclear spectral features are overwhelmed by starlight from their host galaxies. Most of these objects are so distant that their angular diameters are comparable to the slit widths used in ground-based spectroscopic observations. To test our hypothesis, we have obtained integrated spectra of a sample of nearby, well-studied Seyfert 2 galaxies. The data demonstrate clearly that the defining spectral signatures of Seyfert 2s can be hidden by host galaxy starlight.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.