[Seminar] Colloquia 4/21/2009

[Amy Barnes]

Dept of Physics & Astronomy
Lewis Hall 101
Tuesday, April 21st
4:00 pm


Kelly Holley-Bockelmann
Department of Physics and Astronomy
Vanderbilt University

Bars, Stars, and Cuspy Dark Matter Halos

A stellar bar transforms not only a galaxy's disk, but also the dark matter
halo that surrounds the galaxy. We'll discuss the controversial results of
recent high-resolution N-body simulations that show that the central density
of a dark matter halo flattens as the bar torques it. The bar lengthens and
slows as it loses angular momentum, a process that occurs even in rather
warm galaxy disks. This halo and bar evolution is mediated by resonant
interactions between orbits in the halo and the bar pattern speed, as
predicted by a new theory of galaxy dynamics called linear perturbation
theory. We'll review this theory, and discuss its implications and
limitations. Finally, we'll demonstrate that the bar and dark matter halo
response can be critically underestimated for experiments that are unable to
resolve the relevant resonant dynamics. This occurs when the phase space in
the resonant region is under sampled or plagued by noise, which may be a
serious problem for many of today's galaxy dynamics simulations.

ALL GRADUATE STUDENTS ARE REQUIRED TO ATTEND