Unified Seyfert Schemes and the Cosmic X-Ray Background

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Session 53 -- AGN and Radio Galaxies I
Oral presentation, Wednesday, 10:30-12:00, Zellerbach Auditorium Room

[53.01] Unified Seyfert Schemes and the Cosmic X-Ray Background

Piero Madau (STScI)

We have investigated the hard X-ray properties of obscured AGNs as predicted by the popular unification schemes. We consider the reprocessing of X-rays by photoelectric absorption and Compton scattering in cold, Thomson thick material, and compute the transmitted spectra expected for AGNs. We discuss the recent OSSE findings and show that the combination of absorption at low energies, and downscattering together with an intrinsic cutoff in the primary photon distribution at high energies, generates a transmitted spectrum which exhibits a narrow peak in the hard X-ray band. We assess the merits of reprocessed AGNs as the root cause of the XRB. We study the parameter space available to a simple \lq\lq obscuration" model and argue that that a population of heavily self-absorbed AGNs with an exponential cutoff at high energies may plausibly explain the cosmic X-ray background.

Wednesday program listing