Final Mass Loss on the AGB and Planetary Nebula Formation

AGB 和行星状星云形成的最终质量损失

• 批准号: 0806910
• 负责人: Patrick Huggins
• 金额: $ 25.63万
• 依托单位: New York University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-15 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0806910&HistoricalAwards=false
• 关键词: Final; Mass; Loss; AGB; Planetary

This project addresses an important unsolved problem in the evolution of ordinary (1 to 8 solar mass) stars in their transition from the asymptotic giant branch to the planetary nebulae phase: the nature of the final mass loss and the origin of their jets. Enhanced equatorial mass loss and high-velocity jets dominate the early development of planetary nebulae and appear to be nearly ubiquitous, but their origins are unknown. Here, observations of the neutral gas and dust ejected by the stars will be used to address key aspects of this evolutionary phase. 1) The Geometry of AGB Envelopes: Deep imaging will be carried out at optical wavelengths to determine the structure of circumstellar envelopes at the tip of the asymptotic giant branch. The results will be used to determine the long-term evolution of the mass loss geometry leading up to the transition, which provides key constraints on possible jet triggering mechanisms. 2) Jets and Equatorial Tori: Observations will also be made of newly formed jets and tori in proto/young planetary nebulae using ultra high resolution (roughly 0.3 arc sec) millimeter interferometry. Spectro-imaging of the molecular gas will be carried out in lines of 12CO, 13CO, and other molecular species to determine the geometry, mass, and dynamics of the jets and tori, and their inter-relations. The observations will be used to provide general constraints and to test specific scenarios of the final mass loss and jet formation. The results are expected to substantially improve our understanding of this key phase of stellar evolution. This project will impact other fields of astrophysics as planetary nebulae constitute a new class of objects with jets, whose distinct characteristics may offer novel insights on how jets can form. This project also involves the education and research training of graduate and undergraduate students at New York University. It further fosters international scientific co-operation, and forms the basis for Professor Huggins' on-going outreach efforts which are broadly centered on stellar evolution. This includes "Stars in the Curriculum," a collaborative program with an education specialist and practicing teachers, designed to enhance the science curriculum in public schools in New York City.

该项目解决了从渐近巨型分支到行星星云阶段的过渡中普通（1至8个太阳能）恒星演变中的一个重要问题：最终质量损失和喷气机的起源的性质。增强的赤道质量损失和高速射流主导了行星星云的早期发展，似乎几乎无处不在，但它们的起源尚不清楚。在这里，将使用恒星喷射的中性气体和尘埃的观察来解决该进化阶段的关键方面。 1）AGB信封的几何形状：将在光学波长下进行深度成像，以确定渐近巨型分支尖端处的偶尔信封的结构。结果将用于确定导致过渡的质量损失几何形状的长期演变，该几何形状对可能的喷射触发机制提供了关键的约束。 2）喷气机和赤道托里：使用超高分辨率（大约0.3 Arc sec）毫米，也将使用新形成的喷气机和摩托车进行观测。分子气体的光谱成像将以12CO，13CO和其他分子物种的线进行，以确定喷气机和托里的几何形状，质量和动力学及其相互关系。这些观察结果将用于提供一般的约束，并测试最终质量损失和喷气形成的特定情况。预计结果将大大提高我们对恒星进化的关键阶段的理解。该项目将影响其他天体物理学领域，因为行星星云构成了带有喷气机的新物体，其独特的特征可能会提供有关喷气机如何形成的新见解。该项目还涉及纽约大学研究生和本科生的教育和研究培训。它进一步促进了国际科学合作，并构成了Huggins教授持续的外展工作的基础，这些宣传工作广泛地集中在出色的进化上。其中包括与教育专家和教师的合作计划“课程中的明星”，旨在增强纽约市公立学校的科学课程。