ANOMALOUSLY WEAK DYNAMICAL FRICTION IN HALOS

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

Abstract

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.

Keywords

Torque 

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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

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