Probing Circumstellar Disk Properties with Polarization

几乎所有新形成的恒星周围的星周盘都是行星的诞生地，而盘内的物理条件决定着行星的形成。该项目将利用阿塔卡马大型毫米/亚毫米阵列（ALMA）的高质量偏振观测，详细研究附近的星周盘。由于极化机制强烈依赖于波长，极化观测是探测星周盘内子结构和磁场的灵敏手段。利用极化模型，研究人员将探索圆盘极化和由此推断的性质如何随着时间的推移而演变。这个项目的结果将促进天文学家对恒星和行星形成的理解。该项目将训练一名研究生掌握先进的天文技术和应用，为一名本科生提供研究经验，并对美国土著部落进行科学推广。研究小组将利用ALMA进行偏振观测，以测量星周盘的特性，将它们置于系外行星探测的背景下。该研究计划旨在：(1)解决偏振散射测量的最大尘埃颗粒尺寸（~75微米）与光谱指数推断的最大尘埃颗粒尺寸（~毫米）之间的差异；(2)对大样本光源观测到的偏振形态和强度随波长的差异进行表征；(3)在扩大的年轻盘样本中测量偏振，以比较它们与较老的金牛座T盘的性质；(4)探测磁盘磁场或对其施加严格的观测约束。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Circumstellar disks surrounding nearly all newly formed stars are the birthplaces of planets, and the physical conditions within the disks govern the formation of planets. This project will use high quality polarization observations from the Atacama Large Millimeter/submillimeter Array (ALMA) to study nearby circumstellar disks in detail. Because polarization mechanisms depend strongly on wavelength, polarization observations are a sensitive means to probe the substructures and magnetic fields within circumstellar disks. Using polarization models, the investigators will explore how disk polarization and the properties inferred from it evolve over time. Results from this project will advance astronomers’ understanding of star and planet formation. The project will train a graduate student in advanced astronomical techniques and applications, provide research experience to an undergraduate student, and conduct science outreach to a Native American tribe.The research team will undertake polarization observations using ALMA to measure the properties of circumstellar disks, placing them within the context of exoplanet detections. The research program seeks to: (1) address the discrepancy between maximum dust grain sizes measured by polarization scattering (~75 micron) and ones inferred from spectral indices (~millimeter); (2) characterize the differences in observed polarization morphology and intensity with wavelength for a large sample of sources; (3) measure polarization in an enlarged sample of young disks to compare their properties to the older T Tauri disks; and (4) detect disk magnetic fields or place stringent observational constraints on them.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.