Barred Galaxies and Dark Matter: a study of complexity and chaos

Prof. Martin Weinberg (UMass)
February 15, 2018 - 4:00pm


The basic theoretical framework for understanding galaxy formation has
solidified over the past decade but reliable predictions for the
observed galaxy features remains a challenge.  After formation,
galaxies evolve by collective interactions between their disk,
spheroid, and dark-matter halo components. These secular processes
have a profound effect on galactic evolution.  Many of these
interactions are resonantly coupled, have multiple disparate time and
length scales, may be shaped by chaotic behavior, and are, therefore,
very difficult to model by simulation.
I will review the basic dynamics of secular evolution and the standard
canon of established results, using the barred galaxies as a case
study.  Our recent work attempts to reset these dynamics in a
cosmologically-motivated setting.  I will emphasize the importance of
disk-to-halo mass ratios, time-dependent evolution, the sensitivity to
the dark-matter distribution, and the possible connection with chaotic
evolution.  These results lead to predictions for Milky-Way
observations.  Specifically, Gaia should be able to detect the effects
of secular evolution using the phase-space distribution of spheroid
stars.  Similarly, the affects of the bar will dramatically modify the
standard predictions for direct dark-matter detection.