Stellar Dynamics in a Fluctuating Interstellar MediumConfirmed

by Shaunak Modak (Princeton University)

Tuesday Jan 13, 2026, 1:00 PM → 2:30 PM America/Toronto

VIRTUAL ONLY (Perimeter Institute for Theoretical Physics)

The interstellar medium (ISM) plays an important role in sculpting the structure of our Galaxy: in addition to being the birthplaces of stars, ISM substructures have the capacity to significantly perturb stellar orbits. However, conventional stellar-dynamical studies often rely on idealized toy models or omit these gas “fluctuations” entirely, leaving their impact on the evolution of stellar systems poorly understood. In this talk, I will present a model for ISM fluctuations that is both theoretically tractable and easily incorporated into traditional N-body simulations, while retaining the essential features of a realistic ISM. The model is derived from a characterization of the ISM in the state-of-the-art TIGRESS magnetohydrodynamics simulations, which include self-consistent, first-principles gas microphysics and resolve scales down to 2 parsecs. I will then highlight several key differences between the dynamical effects of these realistic fluctuations and those assumed in prevailing models, focusing on orbital heating and radial migration in galactic disks. Finally, I will discuss the importance of accounting for the ISM’s influence in drawing robust conclusions about the Milky Way’s dynamical history and dark matter substructure.