Resolving the Structure of Photodissociation Regions at Low Metallicity

解析低金属丰度下光解离区域的结构

• 批准号: 2308274
• 负责人: Karin Sandstrom
• 金额: $ 40.25万
• 依托单位: University of California-San Diego
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2308274&HistoricalAwards=false
• 关键词: Resolving; Structure; Photodissociation; Regions; Low

Photodissociation regions (PDRs) --- interstellar gas whose properties are determined by far-ultraviolet radiation --- govern the formation of cold, dense, molecular gas where star formation can occur. This research project will use high quality observations from the Atacama Large Millimeter/submillimeter Array (ALMA) to resolve and characterize the different layers of gas within PDRs in the Small Magellanic Cloud (SMC). The processes within PDRs are sensitive to the abundance of heavy elements, and the SMC is poor in heavy elements relative to the Milky Way, so the results from this project will help shed light on how physical conditions within PDRs depend on the “metallicity” of the gas. The project will train a graduate student in methods of advanced astronomical research, and it will develop a program to facilitate the participation of incoming community college transfer students in undergraduate research. The investigators have obtained new ALMA observations that resolve the structure of a PDR in the low metallicity environment of the SMC. They will undertake three efforts to characterize the observed PDR. First, they will measure the temperature of the gas using the rotational emission lines of carbon monoxide (CO) and the fine structure lines of neutral carbon (C), comparing the measurements to PDR models. Next, they will compare the location of the atomic-to-molecular hydrogen (H/H2) transition to the C+/C/CO transition to study the nature of “CO-dark H2 gas” --- PDR layers where hydrogen is molecular (H2) while carbon is either ionized (C+) or neutral. Finally, they will use the high velocity resolution possible with ALMA to study the dynamics and turbulence of gas in the PDR.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.

光解离区域（PDRS）---星际气体的性质是由远离脉络膜辐射确定的 - - 控制可能发生恒星形成的冷，致密，分子气的形成。该研究项目将使用Atacama大毫米/亚毫米阵列（ALMA）的高质量观​​测来解决和表征小麦芽云（SMC）中PDR中不同气体的不同层。 PDR中的过程对重元素的抽象敏感，而SMC相对于银河系的较重元素较差，因此该项目的结果将有助于阐明PDR内的物理条件如何依赖气体的“金属性”。该项目将培训一名研究生的高级天文学研究方法，并将制定一项计划，以促进即将到来的社区大学转学学生参与本科研究。研究人员已经获得了新的ALMA观测值，这些观察结果可以解决SMC低金属性环境中PDR的结构。他们将采取三项努力来表征观察到的PDR。首先，他们将使用一氧化碳（CO）的旋转发射线和中性碳（C）的细胞结构线测量气体温度，将测量结果与PDR模型进行比较。接下来，他们将比较原子能到分子氢（H/H2）向C+/C/CO转变的位置，以研究“ Co-Dark H2 Gas”的性质---碳是分子（H2）的，而碳是离子化（C+）或中性的，而氢是分子（H2）的性质。最后，他们将使用ALMA的高速分辨率来研究PDR中气体的动态和动荡。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响审查了标准，认为通过评估来表现出珍贵的支持。