Dynamical Models for Stars and Gas in Galaxies in the Gaia Era

Coordinators: Jo Bovy, James Bullock, Sukanya Chakrabarti, and Heidi Newberg

Scientific Advisors: Gerry Gilmore, David Hogg, and Kathryn Johnston

The Gaia mission will provide unprecedented data that will help us decipher the puzzle of our Galaxy – how it formed, and how its morphology was shaped by different processes over time. Hydrodynamical, cosmological simulations are now reaching resolutions that are necessary to understand the observed morphology of the Galactic disk. More realistic prescriptions are also being developed to model star formation and feedback in simulations. On the observational side, Gaia and a large number of spectroscopic surveys are providing an enormous wealth of data that can constrain the simulations. It is in this developing context that there is tremendous scope for progress. Not only do we need more sophisticated models to understand the data, observational errors and selection effects have to be incorporated into the models to determine how well a given model matches the data. One of the main goals of our program is to bring together researchers who study spiral structure and bars, gas dynamics, satellites and their tidal streams, and dark matter halos, both in detailed controlled simulations, as well as in cosmological simulations.

The dynamical state of the Galaxy may be more complex than previously thought – recent observations of bulk velocities suggest that the Galaxy may be “wobbling”, and the large-scale ripples and warp in the gaseous outer disk, and plethora of satellite galaxies and stellar tidal streams suggest a multifarious interactional history. The wavelike oscillations that are manifest in the gaseous and stellar disk may lead to a better understanding of bars, spiral arms, and warps – either because these structures cause the observed oscillations, or because they are both caused by the same processes. If the oscillations are caused by dwarf galaxies or dark matter sub-halos, we might be able to use the oscillations to deduce the shape and granularity of dark matter in galactic halos (Galactoseismology) in a way previously not possible. In 2019, the data from Gaia that is necessary to study all these phenomena in detail will be available. Participants in this program will confront their dynamical models with data to establish a detailed, novel picture of the dynamical evolution of the Milky Way.