Dynamical Stability of Cosmological Accretion Disks Embedded in External Radiation Fields : Optically-Thick Case
Cosmological accretion disks (beta disks) driven by the external radiation drag force, which is proportional to the flow velocity, are examined in an optically-thick regime. Assuming an appropriate form of the drag coefficient, which depends upon the optical depth, two branches (optically thin and thick branches) of steady solutions are found. In the very center no steady accretion is realized, because the infall velocity is strongly reduced in the optically thick regions. The dynamical stability of the obtained steady solutions has been investigated using linear analyses. It is found that there are two modes: one is a high-frequency epicyclic mode; the other is a low-frequency secular mode. The former mode exists independent of the optical depths, while the latter mode appears only in optically thick flow. In the Keplerian rotating region it is shown that both modes are "stable" under the local approximation, since the perturbation propagates as a wave having a velocity on the order of the radial infall speed of the unperturbed disk.
- PASJ : publications of the Astronomical Society of Japan
PASJ : publications of the Astronomical Society of Japan 47(4), 425-428, 1995-08-25
Astronomical Society of Japan