Density wakes driving dynamical friction in cored potentials

ABSTRACT Dynamical friction is often modelled with reasonable accuracy by the widely used Chandrasekhar formula. However, in some circumstances, Chandrasekhar’s local and uniform approximations can break down severely. An astrophysically important example ‘core stalling’ phenomenon seen N-body simulations of massive perturber inspiralling into near-harmonic potential a stellar system’s constant-density core (and possibly also direct observations dwarf galaxies globular clusters). In this paper, we use linearized collisionless Boltzmann equation to calculate global response cored galaxy presence perturber. We evaluate density deformation, or wake, due study its geometrical structure better understand stalling. dynamical torque acting on from Lynden-Bell–Kalnajs (LBK) agreement past work, find that force arising corotating resonances greatly weakened, relative formula, inside core. contrast however, population previously neglected high-order non-corotating sustain minimum level frictional at $\sim 10{{\ \rm per\ cent}}$ This suggests complete stalling likely requires phenomena beyond LBK approach; discuss several possible explanations. Additionally, for multiple perturbers, investigate approximate secular interactions (akin Lidov–Kozai dynamics) between two perturbers orbiting system derive criterion instability their close encounters.