Astronomy and Astrophysics – Astrophysics
Scientific paper
2006-10-16
Astronomy and Astrophysics
Astrophysics
19 pages, 16 figures, uses emulateapj, accepted to appear in ApJ. Extensively revised from v1
Scientific paper
10.1086/586882
The predicted central densities of dark matter halos in LCDM models exceed those observed in some galaxies. Weinberg & Katz argue that angular momentum transfer from a rotating bar in the baryonic disk can lower the halo density, but they also contend that N-body simulations of this process will not reveal the true continuum result unless many more than the usual numbers of particles are employed. Adopting their simplified model of a rotating rigid bar in a live halo, I have been unable to find any evidence to support their contention. I find that both the angular momentum transferred and the halo density change are independent of the number of particles over the range usually employed up to that advocated by these authors. I show that my results do not depend on any numerical parameters, and that field methods perform equally with grid methods. I also identify the reasons that the required particle number suggested by Weinberg & Katz is excessive. I further show that when countervailing compression by baryonic settling is ignored, moderate bars can reduce the mean density of the inner halo by 20% - 30%. Long, massive, skinny bars can reduce the mean inner density by a factor ~10. The largest density reductions are achieved at the expense of removing most of the angular momentum likely to reside in the baryonic component. Compression of the halo by baryonic settling must reduce, and may even overwhelm, the density reduction achievable by bar friction.
No associations
LandOfFree
Bar-Halo Friction in Galaxies III: Halo Density Changes does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Bar-Halo Friction in Galaxies III: Halo Density Changes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bar-Halo Friction in Galaxies III: Halo Density Changes will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-243879