Transport of Metals in Galactic Disks and Beyond

宇宙中的物质绝大多数由氢和氦组成，这是大爆炸产生的唯一大量元素。所有较重的元素，天文学家通常称为“金属”，都是由恒星核心的核反应产生的，在这些恒星生命的尽头被喷射出来，然后再循环到下一代恒星和行星中。我们相当了解金属是如何从恒星中形成和喷出的，但对它们在喷出后的路径却知之甚少。这项提案的目的是大大提高我们对这一过程的认识，从而了解构成我们星球和我们身体的元素的生命周期。该项目将涉及计算机模拟金属在星系盘中的流动和可能的流动。在科学界，该项目产生的结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星系盘传输的问题，PI，他的合作者和学生将开展一项模拟孤立剪切盒和整个星系的运动，包括产生不稳定性和传输的各种机制。他们还将模拟超新星发射的银河风，以了解超新星喷出物在进入风的过程中如何与周围的ISM混合。模拟将使用Athena或PENCIL进行孤立的盒子，ENZO用于整个星系和星系风的计算。模拟结果将被纳入一个一维星系演化代码，以研究金属的长期径向分布，并将一维和全三维结果与观测结果进行比较。模拟结果将以参数（例如扩散系数）的形式表示，适用于其他团体在半解析模型或全宇宙学模拟中使用，这些模型缺乏自洽的金属扩散过程建模分辨率，因此必须依赖于亚网格模型。1D星系演化代码也是开源的，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.