Evolution of self-gravitating magnetized disks. I. Axisymmetric simulations

In this paper and a companion work, we report on the first global numerical simulations of self-gravitating magnetized tori, subject in particular to the influence of the magnetorotational instability (MRI). In this work, Paper I, we restrict our calculations to the study of the axisymmetric evolution of such tori. Our goals are twofold: (1) to investigate how self-gravity influences the global structure and evolution of the disks and (2) to determine whether turbulent density inhomogeneities can be enhanced by self-gravity in this regime. As in non-self-gravitating models, the linear growth of the MRI is followed by a turbulent phase, during which angular momentum is transported outward. As a result, self-gravitating tori quickly develop a dual structure composed of an inner thin Keplerian disk fed by a thicker self-gravitating disk, whose rotation profile is close to a Mestel disk. Our results show that the effects of self-gravity enhance density fluctuations much less than they smooth the disk, giving it more coherence. We discuss the expected changes that will occur in three-dimensional simulations, the results of which are presented in a companion paper.