We present two-dimensional numerical simulations of the evolution of a
low-mass star moving supersonically through its surrounding interstellar medium
(ISM). We show that the ejecta of a moving star with a systemic velocity of 20
km/s will interact with the ISM and will form bow-shock structures
qualitatively similar to what is observed. We find that, due to ram-pressure
stripping, most of the mass ejected during the AGB phase is left downstream of
the moving star. As a consequence, the formation of the PN is highly
influenced, even at the low relative velocity of the star. The models are based
on the predictions of stellar evolution calculations. Therefore, the density
and velocity of the AGB and post-AGB winds are time dependent and give rise to
the formation of shock regions inside the cavity formed by the previous winds.
As a result, the stand-off distance is also time dependent and cannot be
determined by simple analytical arguments.Comment: 6 pages, 3 figures, accepted by The Astrophysical Journal Letter