Self-gravity in magnetized accretion discs as a result of a dynamo mechanism with outflows

Abstract

ABSTRACT We investigate the stationary model of a geometrically thin, magnetized accretion disc, which has a dipole-symmetry magnetic field that is produced by an α−ω dynamo and can emanate winds from the disc’s surfaces. Although self-gravity has an important role in the evolution of astrophysical systems, it has been disregarded in many cases, because the equations become more complicated when the mass distribution of the disc is included in the total gravitational potential. In this paper, we consider the effects of self-gravity on the above-mentioned model. It is shown that in the presence of vertical self-gravity, while the magnetic diffusivity decreases, the magnetic field bends and the inflow speed increases. Also, in the inner parts of the disc, mass flux resulting from the wind has a positive value compared with the non-self-gravitating solution, in which all accreted materials are lost. These results can be used for the discs of active galactic nuclei, in which self-gravity is only important in the vertical direction. However, for other types, such as the discs surrounding young stellar objects, self-gravity can be considered in both vertical and radial directions. Here, our analysis of fully self-gravitating discs has revealed that, in this case, the inflow speed depends on the radius. In the model we study, it is also found that the outflows have no effective contribution to the removal of angular momentum for certain radii r ≥ 6R, as is > 60°. However, the system cannot be stabilized by viscous dissipation.