Dynamical self-friction: how mass loss slows you down
  We investigate dynamical self-friction, the process by which material that is
stripped from a subhalo torques its remaining bound remnant, which causes it to
lose orbital angular momentum. By running idealized simulations of a subhalo
orbiting within an analytical host halo potential, we isolate the effect of
self-friction from traditional dynamical friction due to the host halo. While
at some points in a subhalo's orbit the torque of the stripped material can
boost the orbital angular momentum of the remnant, the net effect over the long
term is orbital decay regardless of the initial orbital parameters or subhalo
mass. In order to quantify the strength of self-friction, we run a suite of
simulations spanning typical host-to-subhalo mass ratios and orbital
parameters. We find that the time-scale for self-friction, defined as the
exponential decay time of the subhalo's orbital angular momentum, scales with
mass ratio and orbital circularity similar to standard dynamical friction. The
decay time due to self-friction is roughly an order of magnitude longer,
suggesting that self-friction only contributes at the 10 percent level.
However, along more radial orbits, self-friction can occasionally dominate over
dynamical friction close to pericentric passage, where mass stripping is
intense. This is also the epoch at which the self-friction torque undergoes
large and rapid changes in both magnitude and direction, indicating that
self-friction is an important process to consider when modeling pericentric
passages of subhaloes and their associated satellite galaxies.
