Imaging Linear Polarimetry of Proto-planetary Nebulae: the Origins of Asymmetry

It now seems likely that asymmetries in the circumstellar envelope (CSE) of intermediate mass stars develop during the latter stages of mass outflow as a star approaches the tip of the AGB. These asymmetries in the CSE must in some way give rise to the range of morphologies pbserved in planetary nebulae (PN) and their antecedants proto-planetary nebulae (PPN). We use imaging linear polarimetry to trace scattering in the CSEs and to reveal a morphologically diverse sample of PPN.