From Core to Outflow: Understanding the Driving and shaping of Asymmetric Planetary Nebulae

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AST-0507519Adam FrankUniversity of RochesterFrom Core to Outflow: Understanding the Driving and shaping of AsymmetricPlanetary NebulaeABSTRACTPlanetary nebulae form the linchpin in our understanding of how stars like the Sun die. They are theintermediate evolutionary stage between high mass-loss asymptotic giant branch stars and whitedwarfs. As the final stage of mass loss for low and intermediate mass stars, the nebulae represent acritical step in the mass and chemical evolution cycle for more than half the material ejected into theinterstellar medium. The ubiquity of planetary nebulae and their ease of observation have also madethem premier laboratories for testing new astrophysical theories. Here, a program to betterunderstand the formation of planetary nebulae and the late stages of stellar evolution for low andintermediate mass stars will be undertaken.High resolution images of planetary nebulae and their progenitors have triggered a critical reevaluationof the dominant paradigm for nebular shaping. The new data has revealed features suchas non-axisymmetric episodic jets and multi-polar outflows which can not be embraced with purelyhydrodynamic theories. In addition, data from studies of proto-nebulae show energetic windsforming from cool stars that lack sufficient luminosity for radiative driving. Thus the theory ofplanetary nebula evolution and, by implication, our ideas about processes at work in the late stagesof stellar evolution, require fundamental revision. Previous work by Frank and collaborators hasestablished the potential efficacy of magneto-centrifugal launching processes in planetary nebulaeand proto-planetary nebulae. The central source driving the outflow is either a rapidly rotatingstellar core or a binary-fed accretion disk or both. In all cases the magnetic field is likely tooriginate via dynamo processes. The goals of the present study, which build upon this earlier work,are three fold: (1) To understand the nature of magnetic field generation in single asymptotic giantbranch (pre-nebula) stars, binary systems and in accretion disks. (2) To link magneto-centrifugalprocess at the core (star and/or disk) to global planetary nebulae and proto-nebulae morphologies,kinematics and ionization/chemistry states. This will be achieved through the use of a new AdaptiveMesh Refinement code, AstroBEAR, built at the University of Rochester in collaboration with theUniversity of North Carolina Applied Math Department. (3) And to provide theoretical support foran ongoing series of laboratory astrophysics experiments conducted at Imperial College in Londonwhich have generated supersonic magnetically driven bubbles. These experiments are directlyrelevant to these planetary nebula models.While the work here is focused on planetary nebulae it will be of direct relevance to other fieldsboth theoretically and observationally in the sense of allowing planetary nebulae to potentially actas a test-bed for theories of magnetohydrodynamic outflows. The work with the Imperial Collagegroup helps to deepen the rapidly growing field of High Energy Density Laboratory Astrophysics.The development the AstroBEAR code is of particular benefit as it includes new multi-physics,multi-numerics methods and the work on it here will help train the next generation of computationalastrophysicists. Finally, an innovative outreach program is included which involves the creation ofSci-Interactives: simulation based learning modules which will be posted on popular sciencemagazine websites.