Misc,
Using Torque to Understand Barred Galaxy Models
(2019)cite arxiv:1903.02566Comment: Submitted to MNRAS, comments welcome.
Abstract
We present n-body simulations of barred galaxies to understand the dynamical
mechanisms responsible for the evolution of the bar-disc-dark matter halo
system. We find evidence for three distinct phases of barred galaxy evolution:
assembly, secular growth, and steady-state equilibrium. Using an ensemble
decomposition of the disc into orbital families, we track bar mass, geometry,
and angular momentum through time and correlate the quantities with the phases
of evolution. We follow the angular momentum transfer between particles and
identify the dominant torque channels. We find that the halo model mediates the
assembly and growth of the bar for a high central density halo, and the outer
disc mediates the assembly and growth of the bar in a low central density halo
model. Both galaxies exhibit a steady-state equilibrium phase where the bar is
neither lengthening nor slowing. The steady-state equilibrium results from the
balance of torque between particles that are gaining and losing angular
momentum. We propose observational metrics for barred galaxies that can be used
to help determine the evolutionary phase of a barred galaxy, and discuss the
implications of the phases for galaxy evolution as a whole.
