Transport of Metals in Galactic Disks and Beyond

宇宙中的物质绝大多数是由氢和氦组成的，这是大爆炸产生的唯一大量的元素。所有较重的元素都是由恒星核心的核反应产生的，在这些恒星的生命结束时被抛出，然后循环形成下一代恒星和行星。天文学家将这些元素统称为“金属”。我们相当了解金属是如何从恒星中制造和抛射出来的，但相对较少了解它们在抛射后所走的路径。这项提议的目标是极大地提高我们对这一过程的了解，从而了解构成我们星球和我们身体的元素的生命周期。该项目将涉及对金属流过和可能流出星系盘的计算机模拟。在科学界内，该项目产生的成果将对研究恒星和宇宙学的人有用，该项目本身将有助于培养新一代科学家。这项工作的更广泛影响涉及一个志愿者组织，该组织向圣克鲁斯县监狱的囚犯教授数学和科学。为了解决金属如何通过银盘运输的问题，PI、他的合作者和学生将开展一项运动，模拟孤立的剪切盒和整个星系，包括产生不稳定和运输的各种机制。他们还将对超新星发射星系风进行模拟，以了解超新星喷发出的物质在形成风的过程中如何与周围的ISM混合。对于孤立的盒子，模拟将使用雅典娜或铅笔，对于整个银河系和银河系风的计算将使用恩佐。模拟结果将被纳入一维星系演化代码，以研究金属的长期径向分布，并将一维和全3D结果与观测结果进行比较。模拟结果将以适用于其他小组的参数(例如扩散系数)的形式表示，以便在半解析模型或全宇宙模拟中使用，这些模型缺乏自洽地模拟金属扩散过程的分辨率，因此必须依赖于次网格模型。一维星系演化代码也是开源的，并可供社区使用。这项工作的更广泛影响涉及一个志愿者组织，该组织向圣克鲁斯县监狱的囚犯教授数学和科学。

The matter in the universe is composed overwhelmingly of hydrogen and helium, which were the only elements made in substantial quantities by the big bang. All the heavier elements, which astronomers refer to generically as "metals," were made by nuclear reactions in the cores of stars, ejected at the ends of the lives of those stars, and then recycled into a next generation of stars and planets. We understand reasonably well how metals are made and ejected from stars, but relatively little about the path they take post-ejection. The goal of this proposal is to greatly improve our knowledge of this process, and thereby to understand the life cycles of the elements that make up our planet and our bodies. The project will involve computer simulations of the flows of metals through and potentially out of the disk of a galaxy. Within the scientific community, the results generated by this project will be of use to people studying both stars and cosmology, and the project itself will help train a new generation of scientists. The broader impact of the work involves a volunteer organization which teaches math and science to inmates in Santa Cruz County Jails.To address the question of how metals are transported through galactic disks, the PI, his collaborators, and students will carry out a campaign of simulations of both isolated shearing boxes and entire galaxies, including a variety of mechanisms for generating instability and transport. They will also conduct simulations of the launching of galactic winds by supernovae, in order to understand how supernova ejecta are or are not mixed with the ambient ISM on their way into a wind. The simulations will use either Athena or PENCIL for the isolated boxes, and ENZO for the whole galaxy and galactic wind calculations. The results of the simulations will be incorporated into a 1D galaxy evolution code in order to study the long-term radial distribution of metals, and both the 1D and full 3D results will be compared with observations. The simulation result will be expressed in the form of parameters (e.g. diffusion coefficients) suitable for other groups to use in semi-analytic models or full cosmological simulations that lack the resolution to model metal diffusion processes self-consistently, and thus must rely on subgrid models. The 1D galaxy evolution code is also open source, and is available for use by the community. The broader impact of the work involves a volunteer organization which teaches math and science to inmates in Santa Cruz County Jails.