Published in Re. Prog. Phys. 54 (1991) 579-633. Printed in the UK


ACTIVE GALACTIC NUCLEI

D. E. Osterbrock


Institute for Advanced Study, Princeton, New Jersey 08540, USA


Abstract. Our current knowledge of active nuclei is reviewed. The importance of observational data taken over a wide range of frequencies, from radio and infrared through optical and ultraviolet to x-rays and gamma-rays, is emphasized. Important overall principles include the continuity from quasars and QSOs through Seyfert and radio galaxies to low-luminosity LINERs, the importance of considering roughly cylindrically symmetric (rather than spherically symmetric) structures, and that the various regions generally have different axes and planes of symmetry, and are often warped.


Table of Contents

HISTORICAL INTRODUCTION

OPTICAL SPECTRA
Classification
Diagnostics
Photoionization
Broad-line region
Accretion disk continuum
Ultraviolet line spectra
Temporal variation
Completeness of Seyfert galaxy samples

OTHER WAVELENGTH REGIONS
Radio-frequency spectral region
Infrared continuum
X-ray region
Gamma-ray radiation

TORUS MODEL
Cylindrical symmetry
Seyfert 2s with `hidden' BLRs
Ionization cones

VELOCITY FIELDS
Narrow-line profiles
Extended emission-line region
Overall NLR velocity field
BLR velocity field
Possible magnetic fields

CONTINUITY OF AGN PROPERTIES
QSOs and Seyfert 1 galaxies
Quasars and radio galaxies
Few high-luminosity Seyfert 2s
LINERs

FUELLING
Introduction
Luminosity functions of AGNs
Black holes in normal galaxies
Clusters, groups and neighbor galaxies
Interactions and mergers

EVOLUTION
Fuelling black holes
Formation rate
QSOs in formation

MISCELLANEOUS
Molecular gas
Warmers

CONCLUSION

REFERENCES

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