Flow-Driven Molecular Cloud Formation: An Origin of the Initial Mass Function?

流动驱动的分子云形成：初始质量函数的起源？

• 批准号: 0807305
• 负责人: Lee Hartmann
• 金额: $ 30.03万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0807305&HistoricalAwards=false
• 关键词: Flow; Driven; Molecular; Cloud; Formation

Lee Hartmann, Edwin Bergin, and Fabian Heitsch (University of Michigan) will compute models of flow-driven molecular cloud formation to derive the appropriate initial conditions for star formation. The goal is to generate the turbulent substructure needed to create the dense concentrations which ultimately form stars as a result of various instabilities in post-shock gas, rather than put this substructure in ''by hand''. The turbulence generated by these instabilities will be modified by global flows generated by self-gravity; such flows can produce mid-scale concentrations of mass leading to the formation of star clusters. The program will involve a series of calculations of increasing complexity, including molecule formation and other chemistry, cooling at high densities, self-gravity, and the effects of magnetic fields. Detailed radiative transfer calculations will be employed to compare in detail with observations of molecular clouds.This project will attempt to answer the following questions: Do instabilities which arise naturally in flow-driven molecular cloud formation produce a mass spectrum of dense concentrations consistent with observations of protostellar cores? Do these initial perturbations solely determine the core mass function, or is there significant gravitational merging/coagulation? Is the resulting core spectrum consistent with the stellar initial mass function, or must there be additional fragmentation? How does the environment (metallicities, flow parameters) affect the fragmentation and thus the initial mass function? And how do magnetic fields affect the formation of protostellar cores within flow-formed molecular clouds? These questions are of direct importance to understanding star formation and the origin of the stellar initial mass function.The results of this project will have application to research in the areas of galaxy mergers and star formation at low metallicities because the mechanism of colliding flows is not limited to current Galactic star formation. This project will result in a numerical data set that can be readily compared to observational data of existing or upcoming high-resolution facilities; the simulation results will be made publicly accessible, with analysis tools also provided to extract basic observables. In addition, the numerical projects as well as their results will provide ample training opportunities for undergraduate or graduate student research projects.

Lee Hartmann、Edwin Bergin和Fabian Heitsch（密歇根大学）将计算流动驱动的分子云形成模型，以推导出星星形成的适当初始条件。其目标是产生湍流子结构，以产生密集的浓度，最终形成恒星，作为激波后气体中各种不稳定性的结果，而不是把这个子结构放在“手工”中。这些不稳定性产生的湍流将被自引力产生的全球流动所改变;这种流动可以产生中等规模的质量集中，导致星星团的形成。 该计划将涉及一系列越来越复杂的计算，包括分子形成和其他化学，高密度冷却，自引力和磁场的影响。详细的辐射传输计算将被用来与分子云的观测结果进行详细的比较，本项目将试图回答以下问题：在流动驱动的分子云形成过程中自然产生的不稳定性是否会产生与原恒星核心观测结果一致的高浓度质谱？这些初始扰动是否仅仅决定了核心质量函数，或者是否存在显著的引力合并/凝聚？由此产生的核心光谱与恒星的初始质量函数一致吗？还是必须有额外的碎片？环境（金属丰度、流动参数）如何影响碎裂，从而影响初始质量函数？磁场是如何影响流动形成的分子云中的原恒星核心的形成的？这些问题对于理解星星的形成和恒星初始质量函数的起源有着直接的重要性，因为碰撞流的机制并不局限于当前的银河系星星的形成，所以本项目的结果将应用于星系合并和低金属丰度下星星形成等领域的研究。这一项目将产生一个数字数据集，可以很容易地与现有或即将建立的高分辨率设施的观测数据进行比较;模拟结果将向公众开放，并提供分析工具，以提取基本的可观测数据。此外，数字项目及其结果将为本科生或研究生的研究项目提供充足的培训机会。