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

AST-0507519亚当·弗兰克罗切斯特大学从核心到外流：理解行星状星云的驱动和形成摘要行星状星云是我们理解像太阳这样的恒星如何死亡的关键。它们是介于高质量损失渐近巨星分支星和白矮星之间的中间演化阶段。星云是中低质量恒星质量损失的最后阶段，它代表着质量和化学演化周期中的关键一步，超过一半的物质被喷射到星际介质中。行星状星云的普遍存在和易于观测也使它们成为检验新天体物理学理论的首要实验室。在这里，一个更好地理解行星状星云的形成和中低质量恒星演化的后期阶段的计划将被实施。行星状星云及其前身的高分辨率图像引发了对星云形成的主导范式的批判性重新评估。新资料揭示了非轴对称的幕式喷流和多极外流等纯流体动力学理论所不能涵盖的特征。此外，对原星云的研究数据显示，能量充沛的风是由缺乏足够亮度的冷恒星形成的。因此，行星状星云演化的理论，以及我们关于恒星演化后期过程的想法，都需要进行根本性的修正。Frank和他的合作者以前的工作已经确定了行星状星云和原行星状星云中磁离心发射过程的潜在功效。驱动外流的中心源要么是一个快速膨胀的恒星核心，要么是一个双星吸积盘，或者两者兼而有之。在所有情况下，磁场都可能是通过发电机过程产生的。本研究的目的是建立在这一早期工作的基础上，有三个方面：（1）了解单个渐近巨星分支（前星云）星，双星系统和吸积盘中磁场产生的性质。(2)将核心（星星和/或盘）的磁离心过程与全球行星状星云和原星云的形态、运动学和电离/化学状态联系起来。这将通过使用新的AdaptiveMesh细化代码AstroBEAR来实现，AstroBEAR是由罗切斯特大学与北卡罗来纳州大学应用数学系合作开发的。(3)并为伦敦帝国理工学院正在进行的一系列实验室天体物理学实验提供理论支持，这些实验产生了超音速磁驱动气泡。这些实验与这些行星状星云模型直接相关。虽然这里的工作主要集中在行星状星云上，但在理论和观测上，它与其他领域都有直接的相关性，因为行星状星云可能成为磁流体力学外流理论的试验台。与帝国学院的合作有助于深化快速发展的高能密度实验室天体物理学领域。AstroBEAR代码的开发特别有益，因为它包括新的多物理，多数值方法，这里的工作将有助于培养下一代计算天体物理学家。最后，一个创新的推广计划，其中包括创造科学互动：模拟为基础的学习模块，将张贴在流行的科学杂志网站。

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.