Accretion Disks in Galactic Centers

Summary

ABSTRACT

We present a new model for the dynamics of molecular clouds in the innermost ≈ 200 pc from the Galactic Center. Our analysis allows us to determine the characteristic parameters of the accretion disk as well as the positions of individual clouds with respect to the Galactic Center. Finally, we show that the results are in good agreement with independent determinations of the same parameters and discuss a physical mechanism that allows for the theoretical understanding of these parameters.

OVERVIEW

We assume that the dynamics of accretion disks in the innermost ≈ 200 pc from the Galactic Center (GC) can be modelled in the framework of an accretion disk description. The two parameters that mainly determine the structure of the disk are the radial mass flow rate through the disk (Ṁ) and the dynamical viscosity (v). For a pair of these two parameters, one can calculate the radial velocities (u_s) in the disk with respect to the GC and, consequently, the observable quantity u_x, the radial velocity with respect to the observer (of course, after applying all the relevant corrections). In an iterative process, with this method, we determine the pair (Ṁ, v) that gives the best agreement between the observed and modelled values of v_x. Having found such a solution, we also determined the location of the individual clouds with respect to the GC. Thus, this technique allows us also to construct a map of the distribution of molecular clouds close to the GC. In the next section, we summarize our ansatz for describing the accretion disk.