Dynamical Friction in Cored Galaxies

Some dwarf galaxies like Fornax dwarf Sph containing old globular clusters pose an interesting timing puzzle. The dynamical friction timescales ~ a few Gyrs calculated from the Chandrasekhar formula based on a local theory are too short and imply that these globulars should have already sunk to the center of the host galaxy. This timing problem was solved by N-body simulations which suggest suppression of dynamical friction in cored density profiles of the host. The local theory can not capture this effect and we explore this problem with Tremaine-Weinberg theory which is a global approach and takes into account the real orbital structure of the host galaxy. In this linear response theory, the dynamical friction acts via resonant interactions between perturber and background stars. We show that the number and strength of resonances are reduced inside the core which leads to a suppressed dynamical friction and stalls the evolution of perturber's orbit away from the galaxy center (commonly called "core stalling"). We further explore the density wakes of perturber and find interesting geometrical transformations associated with core stalling.

This talk will be based on these papers:

https://arxiv.org/abs/2112.10801

https://arxiv.org/abs/1810.00369