• 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.




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