Invited Review. Published in The Publications of the
Astronomical Society of the Pacific, Volume 111, pp. 1-30, 1999.
For a PDF version of the article, click
here.
THE ULTRAVIOLET AND OPTICAL CONTINUUM EMISSION IN ACTIVE GALACTIC
NUCLEI: THE STATUS OF ACCRETION DISKS
ANURADHA KORATKAR
Space Telescope Science
Institute, Baltimore, MD 21218;
koratkar@stsci.edu
OMER BLAES
Physics
Department,
University of
California, Santa Barbara, CA 93106;
blaes@vela.physics.ucsb.edu
Abstract.
A fundamental component of models of active galactic nuclei (AGNs) is
an accretion disk around a supermassive black hole. However, the nature
of this accretion disk is not well understood, and current models do
not provide a satisfactory explanation of the optical/UV continuum
observed in AGNs. In this paper we review the substantial theoretical
and observational progress made in the field. We also try to point out
future research directions that would be fruitful in trying to obtain a
complete, self-consistent model of the continuum-emitting regions.
Table of Contents
INTRODUCTION
- EARLY ACCRETION DISK MODELS
- OBSERVATIONS
- The Big Blue Bump
- Lyman Edges
- Polarization
- Fe K
Emission Line
and the Lyman Edge
- Variability
- Microlensing
- Double-peaked Line Profiles
- MORE RECENT ACCRETION DISK MODELS
- The Big Blue Bump
- The Lyman Edge
- Polarization
- ALTERNATIVES TO STANDARD ACCRETION DISKS
- Thick Disks
- Slim Disks
- Advection-dominated Accretion Flows
- Warped Disks
- Optically Thin Emission and Multiphase Flows
- SUMMARY AND DIRECTIONS FOR THE FUTURE
- REFERENCES
