Abstract
In what is defined as Active Galactic Nuclei, the stellar contribution to the emitted light is generally less than (or exceptionally equal to) half the total emitted power. Even if a spectrum of an active galaxy was taken as early as 1908, Seyfert was the first astronomer to understand thatactive galaxiesdo form a class. Seyfert’s original work (1943) listed 12 galaxies, defined at that time asnormal galaxies with high surface brightness nuclei.Spectroscopy then revealed most characteristic properties of Seyfert galaxies, the standard of AGN: acontinuum with both a UV and an IR excess(with respect to usual galaxy continua), together with numerous broad emission lines with high degree of ionization and excitation. Other characteristics of AGN are the following: they have in average large redshifts, some are radio loud, almost all are X-ray emitters, a majority seems to emit in the high-energy range, γ-ray and TeV bands, and many of them present time variability. The discrimination between active galaxies and quasars is mostly historical, due to the very different morphologies of the first Seyferts and quasars. Furthermore, the status of AGN remained unclear for a long time, due to the mixture of morphological and spectroscopic criteria used in many of their first classifications. Since that time, and essentially based on the similarity of their spectra and of most of their properties which vary continuously from the low luminosity less active galaxies to the most luminous quasars.
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Bibliography
Bischof O.B., Becker R.H. 1997, Astron. J. 113, 2000;
Boyle et al. 1988, MNRAS 235, 935
Boyle et al. 1990, MNRAS 243, 1
Boyle et al. 1991 MNRAS 251, 482
Braccesi, A. et al. 1968 ApJ 152, L105
Brinkmann et al. 1997 A&A 319, 413
Buchalter et al. 1998 ApJ 494, 503
Cohen et al. 1996 ApJ 462, L9
Colless et al. 1991 MNRAS 253, 686
Cristiani S. et al. A&A Sup. 112, 347 (1995)
Engels et al. 1998 A&A Sup 128, 507
Engels et al. 1998 A&A Sup 131, 196
Glazebrook et al. 1995 MNRAS 273, 157
Haehnelt & Rees, 1993, MNRAS 263, 168)
Haiman & Loeb, 1997, ApJ 503, 505
Hall et al. 1996 ApJ 462, 614
Hartwick F.&Schade D. 1990 ARA&A 28, 437
Hawkins M. & Véron P. A&A 296, 665 1995
Heckmann, T.M. 1980 A&A 87, 152
Hooper et al. 1995 ApJ 445, 62
Jackson, C.A., Wall, J.V. astro-ph/9808054
Jarvis, R.M., MacAlpine, G.M. 1998 AJ 116, 2624
Koo, D. & Kron, R. 1988 ApJ 325, 92
Malkan M. et al. 1998, ApJ Sup 117, 25
Mathez G. 1976 A&A 53, 15
Mathez G. 1978 A&A 68, 17
Moreau O. and Reboul H. 1995, A&A Sup 111, 169
Peterson B.M. et al. 1998, ApJ 501 82
Peterson B.M. 1997’Active Galactic Nuclei’, Cambridge University Press
Ptak et al. 1998, ApJ 501 L37
Schade D. et al. 1996 MNRAS 278, 95
Schmidt M. 1968 AN 151, 393
Schmidt M. 1970 ApJ 162, 371
Schmidt M. 1972 ApJ 176, 273
Schneider D. et al. 1994 AJ 107, 1245
Shanks T. & Boyle B. 1994 MNRAS 271, 753
Shaver P. et al. 1996 Nature 384, 439
Siemiginowska A. & Elvis M., 1997, ApJ 482, L9
Van der Marel, R.P. astro-ph/9806365
Van Waerbeke L. et al. 1996 A&A 316, 1
Véron-Cetty M.P. and Véron P. 1998, ESO Scientific Report 18
D. W. Weedman 1986’Quasar Astronomy’ Cambridge Astrophysics Series
Yuan W. et al. A&A 330, 108, 1998
Zitelli V. et al. 1992 MNRAS 256
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© 1999 Springer Science+Business Media Dordrecht
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Mathez, G. (1999). Active Galactic Nuclei. In: Lachièze-Rey, M. (eds) Theoretical and Observational Cosmology. NATO Science Series, vol 541. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-4455-1_11
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DOI: https://doi.org/10.1007/978-94-011-4455-1_11
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