There is no commonly accepted or worked-out theory of the AGN outflows. The most developed theory and model calculations were performed by Weymann et al.(1982), Arav and Begelman (1994), Murray and Chang (1997), and by Vilkoviskij et al.(1999). In the last work both wide absorption troughs and line-locking effect were obtained with numerical simulations of UV spectra.
Creation of the general theory of matter outflows from AGN as well as detailed numerical models of the corresponding absorption spectra in the UV and X-ray bands are the main goals of the proposed Project. The scientific value of the theory is very high, because it will give (together with the disk-accretion theory, e.g., Park and Ostriker 2001) a relatively complete picture of the matter dynamics in the vicinity of the AGN engine.
2. Approaches and Specific Problems
2.1. The Interacting Subsystems (IS) Approach: The interacting subsystems approach means that we consider the AGN engine as a complicated physical system, consisting of three main subsystems: the central massive black hole (MBH), the surrounding compact stellar cluster (CSC), and the gas subsystem.The last consists of several components, (i) hot plasma with temperatures from 107 K to 109 K, (ii) imbedded “cold” gas clouds with T ~ 104−105 K, and colder clouds of the so-called obscuring torus (OT). Figure 1 indicates the supposed geometry of the matter distribution around the black hole.
2.2. Structure of the Outflows: We suppose that the outflow of hot gas is generated in the hot corona above the accretion disk. It creates a hot gas wind, which fills the internal hole of the OT. A t the internal surface of the OT the hot-gas wind interacts with the cold clouds of the OT and partly entrains these clouds into the wind. The large clouds fragment into the smaller ones. As a result, a two-phase outflow is produced along a “conical surface” with middle solid angle of the outflow corresponding to the BALQSO part of QSOs. We suppose that the low-ionization BALQSOs are those with line of sights deeply intersecting the OT at the outer part of the conical outflow. On the other hand, the BALs in Seyfert galaxies are produced by wider solid-angle conical outflows with lower velocities. Thus the BAL-AGNs are included into the standard “geometrical unification scheme” (Antonucci 1993) as objects intermediate between AGN-1 and AGN-2. But other geometries of the outflows will be tested as well.
2.3. Gas Dynamics and Radiation Transfer: The gas-dynamic task have to be solved both for the hot gas outflow and the two-phase outflow in the cone. A velocity gradient or shear exists at the outer conical boundary of the flow (the velocity decreases in the transition layer from pure hot gas to the OT interior). In the transition layer, the problem of two-phase gas dynamics demands consideration of the drag forces between the cold clouds and the hot gas, and the radiation pressure forces acting on the cold clouds. For the last force calculations, as well as the absorption coefficients calculations, the problem of the photo-ionization balance in the clouds has to be solved. The radiation transfer calculations must take into consideration the two-phase “cloudy” structure of the moving cold gas. The shortcoming of this approach was the semi-empirical treating of the hot gas heating (Vilkoviskij et al. 1999). So the important problem which have to be solved is relation of the gas outflows and jets, especially as this problem is connected with the well-known puzzle of the radio quiet/loud dichotomy of AGNs. For this purpose the magnetohydrodynamic theory will be involved.
Outflows and Jets from AGN Disks
In the proposed work we plan to study: (1) The collimating effect of having the outflow propagate into a pre-existing hot gas distribution above the disk. This mechanism of collimation was investigated theoretically by Lovelace et al. (1991). (2) The entrainment and acceleration of the hot gas in the direction perpendicular to the disk. And, (3) The modification of our Godonov-type axisymmetric MHD code to include special relativistic effects.