Dynamics of an interacting luminous disk, dark halo, and satellite companion

This paper explores the dynamical interaction between extended halo and spheroid components of a disk galaxy and an environmental disturbance. One finds that resonant interaction between a galaxy and passing interlopers or satellite companions can carry the disturbance inward, deep inside the halo, where it can perturb the disk. Applied to the Milky Way for example, the LMC and SMC appear to be sufficient to cause the observed Galactic warp and possibly seed other asymmetries. A polar satellite orbit produces the largest warp and therefore the inferred LMC orbit is nearly optimal for maximum warp production. Both the magnitude and morphology of the response depend on the details of the disk and halo models. The results and prognosis for N-body simulations are discussed. Discreteness noise in the halo, similar to that due to a population of $10^6M_\odot$ black holes, can produce observable warping.