Invited highlight talk at the 7th INTEGRAL Workshop, September 8-11, 2008. Copenhagen, Denmark.
astro-ph/0902.3033

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THE PEAK REGION OF THE EXTRAGALACTIC BACKGROUND RADIATION

Marco Ajello


Stanford Linear Accelerator Center, 2575 Sand Hill Road, Menlo Park, CA 94025 and KIPAC, 2575 Sand Hill Road, Menlo Park, CA 94025
E-mail: majello@slac.stanford.edu


Abstract. The Cosmic X-ray background carries the information of cosmic accretion onto super-massive black holes. The intensity at its peak can be used to constrain the integrated space density of highly obscured AGNs. Determining the shape and intensity of the Cosmic X-ray background radiation represents, however, a first step towards the understanding of the population of Compton-thick AGNs. The study of AGNs in the local and more distant Universe allows to understand the whole picture. In this talk, I will review the current understanding of generation of the Cosmic X-ray background at its peak. I will focus on the recent measurements of the Cosmic X-ray background and I will discuss the recent advancements in the understanding of AGNs in both the local and more distant Universe. Finally, I will also discuss open issues and future prospects.


Keywords Astrophysics - Cosmology and Extragalactic Astrophysics


Table of Contents

INTRODUCTION
History of the Cosmic X-ray background
Constraints from the Cosmic X-ray background

ADVANCES IN THE MEASUREMENT OF THE COSMIC X-RAY BACKGROUND

HARD X-RAY SURVEYS
The role of absorption
Compton-thick AGNs in the local Universe
Compton-thick AGNs in the high-z Universe

REFLECTION AND CUT-OFF PROPERTIES OF AGNs

UNVEILING THE HARD X-RAY SKY: THE SIX SURVEY

CONCLUSIONS

REFERENCES

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