SIMBAD references

We have carried out 3D hydrodynamic simulations of a precessing jet/counterjet ejection. We have included the photoionization from the central source, considering three different ionizing photon rates (S_*=10⁴⁵, 10⁴⁶, and 10⁴⁷ phots s^–1), in order to determine its effect on the morphology and kinematics of the protoplanetary nebula. We have considered a time-dependent ejection density that generates dense knot structures in the jet, which are then partially photoionized by the ionizing photon field from the central source. We also explore the role of the medium in which the jet is propagated, under these conditions. The photoionization results in a larger Hα emission of the knots, and in an acceleration of the knots as a result of the so-called "rocket effect." We find that for larger values of the ionizing photon rate, a clear outwards acceleration of the knots is produced. These models are appropriate for explaining protoplanetary nebulae in which such outwards accelerations are observed.