pPNe: Lobe-Shaping Models & HST Images

Other conference contribution, 2014

HST images of some 50 pre planetary nebulae ("pPNe") are now available. A confrontation of images with theoretical shaping models is timely in order to determine whether one of the paradigms emerges as a best fit. The near-nuclear morphologies of twelve HST images of symmetric, bright, and well-resolved pPNe are compared to predictions of four basic types of simulations of collimated outflows. Diverging (or conical) outflows and magnetically launched winds generally provide a satisfactory morphological for the many pPNe whose lobes are edge brightened or open. Axial, or "cylindrical" flows (i.e., thin jets or clumps) nicely explain the formation of those lobes in pPNe with terminal bow shocks or spiral patterns inscribed on their edges. The review covers the past decade of HST imaging and related numerical modeling with an eye on future ALMA kinematic imaging.