Conference proceedings to appear in "The Central Engine of Active Galactic Nuclei", ed. L. C. Ho and J.-M. Wang (San Francisco: ASP) 2007
astro-ph/0701109

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X-RAY ABSORPTION IN ACTIVE GALACTIC NUCLEI

Roberto Maiolino 1 and Guido Risaliti 2


Abstract: We review some of the main physical and statistical properties of the X-ray absorber in AGNs. In particular, we review the distribution of the absorbing column density inferred from X-ray observations of various AGN samples. We discuss the location of the X-ray absorber and the relation with the dust absorption at optical and infrared wavelengths. Finally, we shortly review the recent findings on X-ray absorption at high luminosities and at high redshift.


Table of Contents

INTRODUCTION

THE WARM ABSORBER

COLD ABSORPTION: GENERAL PROPERTIES AND WARNINGS

THE NH DISTRIBUTION AMONG AGNs

THE LOCATION OF THE COLD X-RAY ABSORBER

X-RAY ABSORPTION VERSUS OPTICAL AND INFRARED ABSORPTION

X-RAY ABSORPTION AT HIGH LUMINOSITIES AND AT HIGH REDSHIFT

OPEN ISSUES

REFERENCES



1 INAF - Astronomical Observatory of Rome, Italy
2 INAF - Arcetri Astrophysical Observatory, Firenze, Italy

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