Active Galactic Nuclei a

  title={Active Galactic Nuclei a},
  author={Donald E. Osterbrock},
  journal={Annals of the New York Academy of Sciences},
  • D. Osterbrock
  • Published 1 March 1984
  • Physics
  • Annals of the New York Academy of Sciences
Recent observational and theoretical investigations of AGN are reviewed. The basic AGN characteristics (broad emission lines of abundant ions, X-ray emission, and a sharp starlike appearance) are summarized, and particular attention is given to the spectral classification of Seyfert galaxies, the AGN velocity fields and their measurement, low-ionization narrow-emission-line regions (LINERs), observations supporting a torus model of Seyfert AGN, extended gas and ionization, and the black-hole… 
X-ray emission mechanisms in active galactic nuclei
Active Galactic Nuclei (AGN) are compact regions at the centre of active galaxies which are visible across the full electromagnetic spectrum. Their radiation comes from the accretion of matter onto a
Accretion Disks in Active Galactic Nuclei a
The black-hole/accretion-disk model proposed to explain the high observed luminosities of AGN is discussed, reviewing the results of recent observational and theoretical investigations. The
Optical/ultraviolet continuum emission theory in radio quiet quasars and active galactic nuclei
Accretion disk models still do not provide a satisfactory explanation of the optical/ultraviolet continuum observed in Seyferts and quasars. Substantial theoretical progress has been made in
High energy emission from galactic jets
In this chapter we review some aspects of X-ray binaries, particularly those presenting steady jets, i.e. microquasars. Because of their proximity and similarities with active galactic nuclei (AGN),
Physics and Kinematics of the Extended Narrow Line Region of Three AGN
ln this work I will study the physicaland kinematic properties of the Extended Narrow Line Region (ENLR) of three Active Galactic Nuclei (AGNs). The ENLR is a structure which can be observed in
Broad band properties of radio-loud emission line AGNs
Recent BeppoSAX observations of bright radio galaxies have shown that they have a considerable variety of spectral properties and important differences with respect to Seyfert galaxies. Reprocessing
The structure and radiation spectra of illuminated accretion disks in AGN: II. Flare/spot model of X-ray variability
We discuss a model of the X-ray variability of active galactic nuclei (AGN). We consider multiple spots that originate on the surface of an accretion disk following intense irradiation by coronal
22 Active Galactic Nuclei
X-ray observations of active galactic nuclei (AGN) are of wide astrophysical interest. The amount and efficiency of the energy release within the immediate neighbourhood of black holes belong to the
The kpc-scale radio source population
We are conducting a multi-wavelength (radio, optical, and X-ray) observational campaign to classify, morphologically and physically, a sample of 55 flat-spectrum radio sources dominated by structure
On the Nature of X-Ray-Bright, Optically Normal Galaxies
Recent X-ray surveys by Chandra and XMM-Newton have revealed a population of X-ray-bright, optically normal galaxies (XBONGs) at moderate redshifts. We propose that many XBONGs are powered by an


Low-ionization active galactic nuclei: X-ray or shock heated?
We evaluate narrow-line ratios for a wide variety of active galactic nuclei, including those claimed to be shock heated. In the context of a Seyfert photoionization model, the entire range of
Active galactic nuclei and quasars, because of their large luminosities, apparently larger than can be accounted for by nuclear reactions in the stars involved, are generally considered subjects
Galaxy mergers and active nuclei. I. The luminosity function. II. Cosmological evolution
Galaxy mergers may boost the tidal disruption rate of stars near a massive central black hole in the nucleus of a galaxy, producing active galactic nuclei (AGNs) with nonthermal luminosities up to
Seyfert galaxy narrow-line regions. II - Kinematic models
A class of kinematic models for the narrow-line regions of active galactic nuclei is presented. The models incorporate continuity-constrained radial flow of emitting material in a bounded, spherical
Classification parameters for the emission-line spectra of extragalactic objects
An investigation is made of the merits of various emission-line intensity ratios for classifying the spectra of extragalactic objects. It is shown empirically that several combinations of
3C 273 : A Star-Like Object with Large Red-Shift
In the early 1960s, astronomers were puzzled by quasars — sources of intense radio emission that seemed to be stars, but had unintelligible optical spectra. In 1963, Maarten Schmidt solved the puzzle
Thick accretion disks with super-Eddington luminosities
We describe a Newtonian version of the theory of thick accretion disks orbiting black holes. In view of the present inadequate knowledge of microscopic viscosity process, this theory adopts a
The effects of interactions on spiral galaxies. I - Nuclear activity and star formation
We present results of spectrophotometry of the nuclei of 161 (mostly spiral) galaxies with bright companions, and emission-line imaging of 63 galaxies. The program includes a complete sample,
Seyfert galaxy narrow-line regions. I - Observations of forbidden O III lambda 5007
High-resolution (23 km/s) spectra of the forbidden O III emission line at 500.7 nm from the nuclear regions of 32 Seyfert galaxies and low-redshift QSOs have been obtained at the Smithsonian
Thermal continuum from accretion disks in quasars
ACCRETION onto black holes in galactic nuclei is a promising power source for quasars1,2, but observational proof has been elusive. I argue here that supermassive accretion in disks may explain the