• J. A. Sellwood
  • Victor P. Debattista
Part of the Astrophysics and Space Science Proceedings book series (ASSSP)


A bar rotating in a pressure-supported halo generally loses angular momentum and slows down due to dynamical friction. Valenzuela & Klypin report a counter-example of a bar that rotates in a dense halo with little friction for several Gyr, and argue that their result invalidates the claim by Debattista & Sellwood that fast bars in real galaxies require a low halo density. We show that it is possible for friction to cease for a while should the pattern speed of the bar fluctuate upward. The reduced friction is due to an anomalous gradient in the phase-space density of particles at the principal resonance created by the earlier evolution. The result obtained by Valenzuela & Klypin is probably an artifact of their adaptive mesh refinement method, but anyway could not persist in a real galaxy. The conclusion by Debattista & Sellwood still stands.


Dynamical Friction Phase Space Density Frictional Torque Pattern Speed Principal Resonance 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Binney, J. & Tremaine, S. 1987, Galactic Dynamics (Princeton: Princeton University Press)MATHGoogle Scholar
  2. Debattista, V. P. & Sellwood, J. A. 1998, Ap. J. Lett., 493, L5CrossRefADSGoogle Scholar
  3. Debattista, V. P. & Sellwood, J. A. 2000, Ap. J., 543, 704CrossRefADSGoogle Scholar
  4. Hernquist, L. 1990, Ap. J., 356, 359CrossRefADSGoogle Scholar
  5. Holley-Bockelmann, K., Weinberg, M. D. & Katz, N. 2003, astro-ph/0306374Google Scholar
  6. Holley-Bockelmann, K. & Weinberg, M. D. 2005, DDA abstract 36.0512Google Scholar
  7. Kalnajs, A. J. 1977, Ap. J., 212, 637CrossRefADSGoogle Scholar
  8. Kravtsov, A. V., Klypin, A. & Khokhlov, A. M. 1997, Ap. J. Suppl., 111, 73CrossRefADSGoogle Scholar
  9. Lin, D. N. C. & Tremaine, S. 1983, Ap. J., 264, 364CrossRefADSGoogle Scholar
  10. Lynden-Bell, D. 1979, MNRAS, 187, 101MATHADSGoogle Scholar
  11. Lynden-Bell, D. & Kalnajs, A. J. 1972, MNRAS, 157, 1ADSGoogle Scholar
  12. Sellwood, J. A. 2003, Ap. J., 587, 638CrossRefADSGoogle Scholar
  13. Sellwood, J. A. 2004, astro-ph/0407533Google Scholar
  14. Tremaine, S. & Weinberg, M. D. 1984, MNRAS, 209, 729MATHADSMathSciNetGoogle Scholar
  15. Valenzuela, O. & Klypin, A. 2003, MNRAS, 345, 406CrossRefADSGoogle Scholar
  16. Weinberg, M. D. 2004, astro-ph/0404169Google Scholar
  17. Weinberg, M. D. & Katz, N. 2002, Ap. J., 580, 627CrossRefADSGoogle Scholar

Copyright information

© Springer 2007

Authors and Affiliations

  • J. A. Sellwood
    • 1
  • Victor P. Debattista
    • 2
  1. 1.Department of Physics & AstronomyRutgers UniversityPiscatawayUSA
  2. 2.Astronomy DepartmentUniversity of WashingtonSeattleUSA

Personalised recommendations