Universal spectral shape of high accretion rate AGN

Free access article

Issue		A&A Volume 412, Number 2, December III 2003


Page(s)		317 - 329
Section		Cosmology
DOI		http://dx.doi.org/10.1051/0004-6361:20031441

A&A 412, 317-329 (2003)
DOI: 10.1051/0004-6361:20031441

Universal spectral shape of high accretion rate AGN

B. Czerny¹, M. Nikolajuk¹, A. Rózanska¹, A.-M. Dumont², Z. Loska¹ and P. T. Zycki¹

¹ Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland
² Observatoire de Paris-Meudon, DAEC, Meudon, France

(Received 21 March 2003 / Accepted 14 August 2003)

Abstract
The spectra of quasars and NLS1 galaxies show surprising similarity in their spectral shape. They seem to scale only with the accretion rate. This is in contradiction with the simple expectations from the standard disk model which predicts lower disk temperature for higher black hole mass. Here we consider two mechanisms modifying the disk spectrum: the irradiation of the outer disk due to the scattering of the flux by the extended ionized medium (warm absorber) and the development of the warm Comptonizing disk skin under the effect of the radiation pressure instability. Those two mechanisms seem to lead to a spectrum which indeed roughly scales, as observed, only with the accretion rate. The scenario applies only to objects with relatively high Eddington ratio for which disk evaporation is inefficient.

Key words: radiative transfer -- accretion disks -- galaxies: active -- galaxies: Seyfert -- X-rays: galaxies

Offprint request: B. Czerny, bcz@camk.edu.pl

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