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Astron. Astrophys. 327, 57-60 (1997)

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1. Introduction

Studies of the broad emission lines in AGN have attracted very large numbers of Astronomers. It is commonly admitted that the accretion disk model is a possible and successful theory to explain the line and continuum emission. Several spectral features of the AGN, such as the continuum excess in the UV and the broad line spectrum, involving different physical processes of emission (thermal for the UV continuum, photoionization for the line sprectrum) have been proposed as signatures of the disk. Schield (1977) was the first to show that the broad line emission can be induced in AGN by the illumination of an accretion disk at a distance of [FORMULA] gravitational radii (Jones & Raine 1980; Raine & Smith 1981). This possibility has been explained later by Begelman and Mckee (1983) and by Mardaljevic et al.(1988). Collin-Souffrin and Dumont (1987I, 1990II, 1990III, 1990IV, hereafter CSD) have done a lot of research on the line and continuum emission from the outer region of accretion disks in AGN, and gotten several interesting and important results. CSD pointed out that the amount of energy available in the HI zone from which the bulk of the Bulmer lines and the FeII, MgII, and CII lines are emmitted depends on the column density N of the medium, the typical radii (such as [FORMULA]), and correct opacities. However, all the parameters which are related to the line and continuum formations are involved with the structure of accretion disk. So a self-consistent structure of accretion is necessary for explaining the line and continuum spectra.

It is well known that the magnetic field can play an important role in accretion disks(Galeev et al.1979, Blandford & Payne 1982,Yang et al.1995). Field and Rogers (1993) explained the spectral emission from far infrared to X-ray with a magnetized accretion disk in AGN. Self-gravitation of an accretion disk have a bigger influence on the vertical and radial disk structure (Paczynski 1978; Yang et al. 1990; Storzer 1993). Sakimoto et al.(1981) and Schneider (1996) examined the structure and the stability of magnetized accretion disk with self-gravitation, but Sakimoto and Schneider did not discussed the effects of magnetic field and self-gravitation on the line and continuum emission

In this paper, we adopted the CSD's method (1990II), and extended Sakimoto's model (1981) to investigate the structure of self-gravitation and magnetized accretion disk, which is important to discuss the line and continuum emission from the outer region of the disk. We derive the scale height, central density, and central temperature, as well as the column density,and several typical radii of the disk. we also compared our results with the work by CSD (1990II). In Sect. 2, we present the basic equations of magnetized accretion disk with self- gravitation. We give the results in Sect. 3, and discuss them in Sect. 4.

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© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998