Astron. Astrophys. 337, 105-112 (1998)

Angular momentum transport in the central region of the Galaxy

Leonid M. Ozernoy ^{1, 2}, Alexei M. Fridman ^{3, 4} and Peter L. Biermann <sup>5

1</sup> Computational Sciences Institute and Department of Physics & Astronomy, George Mason U., Fairfax, VA 22030-4444, USA (ozernoy@science.gmu.edu)
² Laboratory for Astronomy and Solar Physics, Goddard Space Flight Center, Greenbelt, MD 20771, USA (ozernoy@stars.gsfc.nasa.gov)
³ Institute of Astronomy, Russian Academy of Sciences, 48 Pyatnitskaya St., 109017 Moscow, Russia (afridman@inasan.rssi.ru)
⁴ Moscow State University, 18 University Prospect, 119899 Moscow, Russia
⁵ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, P.O. Box 2024, D-53010, Germany (p165bie@mpifr-bonn.mpg.de)

Received 30 April 1996 / Accepted 22 April 1998

Abstract

We discuss mechanisms for angular momentum transport in the clumpy medium of the circumnuclear disk at the Galactic center. The viscosity due to clump-clump collisions is found to be less than some critical viscosity; this meets the conditions at which a collective mode of nonaxisymmetric shear perturbations in the disk is able to grow until going into the saturation regime where fully developed turbulence is established. We find that the angular momentum transfer due to this turbulent viscosity turns out to comparable to the transport due to magnetic torques. Taken together, the turbulent and magnetic transfer of angular momentum are able to provide the inflow of mass into the central parsec with a rate of about  , consistent with the available data.

Key words: Galaxy: center accretion, accretion disks turbulence ISM: clouds ISM: kinematics and dynamics

Send offprint requests to: L. Ozernoy

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Contents

• 1. Introduction
• 2. Viscosity due to cloud-cloud interactions
• 3. Small-scale turbulent viscosity
  • 3.1. Non-viscous case ()
  • 3.2. General case (non-zero viscosity)
• 4. Viscosity in the circumnuclear ring
• 5. Discussion
• Acknowledgements
• Appendix
  • Appendix A: shear viscosity in a clumpy disk at elastic/inelastic encounters
  • Appendix B: character of perturbations in a differentially rotating vs. a solid-body rotating disk
  • Appendix C: Velocity perturbations in a plane shear layer
• References

© European Southern Observatory (ESO) 1998

Online publication: August 6, 1998
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