A stringent test of the galaxy formation paradigm: detailed modeling of the dynamics and stellar population of the Milky Way

高红移和低红移观测与数值模拟相结合，在过去30年中提供了一种情景，在暗物质(DM)引力坍塌的推动下，星系形成以分级方式进行。尽管这一情景解释了大部分观测结果，但其最有力和最清晰的预测仍有待证实：(I)星系预计将被嵌入大质量Dm光晕中，然而，值得注意的是，Dm的存在本身仍存在争议，引力定律不是爱因斯坦定律的可能性仍在讨论中。(2)星系的分级结构预计将在暗物质和发光物质中留下非常大量的子结构。尽管附近星系中存在一些子结构，但这并没有达到预期的水平。(3)星系形成模型对星系亚结构的年龄和化学成分进行了详细的预测，但这些信息很难从星系观测中提取出来。由于其邻近区域，我们的银河系构成了一个独特的实验室，可以对星系形成模式进行上述严格的观测测试。对于我们的银河系来说，实际上可以很容易地观察到单个恒星，并且原则上可以获得位置和速度。这些恒星可以作为重力的示踪剂，准确地检测DM的存在。单个恒星的化学成分也可以被测量，并可以结合恒星运动学来发现银河系中的恒星亚成分。然而，到目前为止，还没有这样的数据存在。情况很快就会发生戏剧性的变化。来自地面(RAVE，SEGUE)和太空(GAIA)的一些正在进行的大型观测调查将测量我们银河系中大部分恒星的位置和速度。这将是自四个世纪前伽利略用望远镜观察银河系以来，我们对银河系认识的最大改进，当时伽利略首次意识到它实际上是由单个恒星组成的。这些新数据具有类似的潜力，可以彻底改变我们对星系形成的理解。我提议的项目的主要目标是通过构建我们银河系的动力学和化学成分的详细模型，对星系形成范式进行上述三项严格的测试，并与RAVE、SEGUE和GAIA调查提供的位置、速度和化学成分的恒星测量结果进行比较。

High and low-redshift observations, in combination with numerical simulations, have provided a scenario, over the last 30 years, in which galaxy formation proceeds in a hierarchical fashion, driven by the gravitational collapse of dark matter (DM). Although the scenario explains most of the observations, its strongest and cleanest predictions still have to be confirmed: (i) galaxies are expected to be embedded in massive DM halos, however, remarkably, the very existence of DM is still debated and the possibility that the laws of gravity are not those of Einstein is under discussion. (ii) the hierarchical build up of galaxies is expected to leave behind a very large number of substructures, in both the dark and luminous matter. Although some substructure in nearby galaxies exists, this is not at the expected level. (iii) galaxy formation models make detailed prediction about the age and chemical composition of galactic substructure, but these information are difficult to extract from galaxy observations. Due to its vicinity, our Milky Way constitute a unique laboratory to perform the above stringent observational tests of the galaxy formation paradigm. For our Galaxy in fact individual stars can be easily observed, and position and velocity can in principle be obtained. The stars could be used as tracers of the gravity to accurately detect the presence of DM. The chemical composition of individual stars can also be measured, and could be used, in combination with the stellar kinematics, to uncover stellar subcomponents in the Galaxy. However until now no such data existed. The situation is soon going to change dramatically. A number of ongoing large observational survey from the ground (RAVE, SEGUE) and from space (Gaia) will measure position and velocities for a large fraction of all the stars in our Galaxy. This will provide the biggest improvement in our knowledge of the Galaxy, since Galileo observed it with its telescope, four centuries ago, first realizing that it was actually made of individual stars. The new data have a similar potential to revolutionize our understanding of how galaxies form. The main goal of my proposed project is to perform the above three stringent tests of the galaxy formation paradigm, by constructing a detailed model of the dynamics and the chemical composition of our Milky Way, to be compared with the position, velocity and chemical composition stellar measurements provided by the RAVE, SEGUE and then Gaia survey.