SIMBAD references

We investigate, from both analytical and numerical points of view, the formation of stagnation features in precessing Herbig-Haro type jets. These structures are formed via a mechanism very similar to that recently presented as a formation mechanism for fast low-ionization emission regions (FLIERs) in planetary nebulae. It is found that a precessing jet advances as a complex function of time; however, we derive a simple iterative formula for the propagation rate of the jet. We also derive a condition for the likely formation of stagnation features based on an approximate structure of the leading bow shock. These results compare well with full 3D numerical simulations of precessing jets. In a comparison with observations we are able to offer qualitative explanations for several discrepancies between theory and observation, e.g. the lack of `garden hose' expansion observed in the HH43 jet (recently suggested to precess), and the presence of high velocity clumps (~100km.s^–1), apparently being overrun by a faster wind in the HH29 complex.