Galactic Structure and History with chemodynamical models

在未来三年内，欧空局的盖亚任务将开始提供大约10亿颗恒星的三维位置和正常运动样本，比之前的任何目录都要大1万倍。与此同时，大规模的光谱调查正在产生关于恒星化学成分和年龄的详细信息。这两项调查是互补的：盖亚的运动学告诉我们银河系现在的结构和动力学，而丰度的信息揭示了恒星诞生的地方。牛津大学在开发化学动力学建模工具方面发挥着主导作用，这些工具用于从这些数据推断银河系的当今结构和过去的历史。就在5年前，我们发现径向迁移在形成银河系的过程中起着关键作用：当恒星经历了经过的螺旋臂的旋转潜力时，它们的角动量和星系中心半径会发生很大的变化，这在圆盘中引起了比以前的朴素模型更多的化学混合。然而，对像银河系这样的螺旋星系的定量影响却知之甚少。自然，该项目包括两个阶段：主要是在前1.5年的理论工作，以提高对径向迁移和圆盘加热的理解，以及将这些改进的模型应用于该博士项目中期的第一次Gaia数据发布。该生目前的工作计划如下：截止2016年1月，前三个月学习相关文献和背景知识，重点研究银河动力学、化学演化和先进统计方法。此外，学生将接受编程技能的培训，特别是c++。在此之后，学生将学习使用小组内现有的软件，包括化学动力学模型和我们先进的光谱代码，这些代码将在稍后为建模提供输入。该学生将致力于提高对相关过程（径向迁移、加热、更好地理解化学富集）的分析理解，并探索即将发布的盖亚数据预测的可行性和稳健性。在第一个阶段，我们已经从调查（Apogee, Gaia-ESO， SEGUE， RAVE， GCS等）中获得了大量数据，这些数据用于培训，并可能提供初步见解和出版物。第一个项目将是约束APOGEE、RAVE和SEGUE调查中与圆盘结构相关的运动学像差。在第二部分，我们将测量银河系的参数和星系结构对盖亚测量的太阳附近的详细影响。根据学生的专业水平、技能和兴趣的发展，项目范围将在更多的理论工作之间进行调整，以新的方式了解我们银河系的物理学，以及使用小组内现有工具进行数据分析。

Within the next three years, ESA's Gaia mission will start to provide three-dimensional positions and proper motions a sample of around a billion stars, ten thousand times larger than any previous catalogue. Concurrently, large-scale spectroscopic surveys are producing detailed information on the chemical composition and ages of stars. The two surveys are complementary: the Gaia kinematics tell us about the present-day structure and dynamics of the Galaxy, while the abundance information reveals where stars were born. Oxford plays a leading role in developing the chemodynamical modelling tools used to infer the present-day structure and past history of the Galaxy from such data. Only 5 years ago we discovered that radial migration plays a key role in shaping the Galaxy: when stars experience the rotating potential of a passing spiral arm, they undergo large changes in angular momentum and Galactocentric radius, which induces much more chemical mixing in the disc than previous naive models. Yet, the quantitative effects on spiral galaxies like the Milky Way are poorly known.Naturally, this project encompasses two phases: Mostly theoretical work to improve the understanding of radial migration and disc heating in the first 1.5 years, and application of these improved models to the first Gaia data release mid-term of this PhD project.The current work plan for the student is as follows: Study of the relevant literature and background knowledge for the first three months until Jan 2016, focussing on Galactic dynamics, chemical evolution and advanced statistical methods. Also, the student will be trained in programming skills, in particular C++. After this, the student will learn to use the existing software within the group, including chemodynamic models and our advanced spectroscopic code, which will later provide inputs for the modelling. The student will work on an improved analytic understanding of the involved processes (radial migration, heating, better understanding of chemical enrichment) and explore the viability and robustness of predictions for the imminent Gaia data release. During this first period we already have an abundance of data from surveys (Apogee, Gaia-ESO, SEGUE, RAVE, GCS, etc.), which serve for training and may deliver first insights and publications. A first project will be to constrain kinematic aberrations relating to disc structure in the APOGEE, RAVE, and SEGUE surveys.In the second half we will measure Galactic parameters and detailed effects of Galactic structure on the solar neighbourhood as measured by Gaia. Depending on the level of expertise, skills and interests developed by the student during, the project scope will be tailored between more theoretical work on new ways to understand the physics of our Galaxy, and data analysis using the existing tools within the group.