Multi-scale simulations of the Universe

我们在萨里大学的新团队拥有广泛的计算和动力学专业知识，从围绕凹陷A*运行的恒星到宇宙的宇宙学模拟。通过第一次将这些不同的尺度联系在一起，我们试图阐明现代天体物理学中的关键悬而未决的问题：-大质量黑洞(BH)双星是如何合并的？暗物质的性质是什么？(p2；p3)；星系是如何形成的？球状星团是如何形成的？大质量恒星是如何形成的？(P6)同时，我们将建立一个社区模拟数据库，以：(I)为即将到来的ELISA、GAIA、ALMA、Euclid和SKA任务提供模拟数据；以及(Ii)指导我们对这些新的和令人兴奋的数据的理论理解。在p1中，我们研究超大质量黑洞在银河中心的合并。虽然每个大质量星系似乎都有一个超大质量黑洞，但从未见过近距离的双星黑洞对。了解这样的双星如何合并以及为什么合并对于星系凸起的形成和演化非常重要，因为这样的合并会产生整个宇宙都可见的引力波。在这个项目中，我们将首次详细研究四种聚结机制的联合效应，其中一种机制是全新的。在p2和p3中，我们将探索暗物质的性质。暗物质是一种看不见的物质，似乎构成了宇宙的大部分引力质量，但它仍然是个谜。在p2中，我们使用了一种新的数值技术来模拟暗物质流体，以对暗物质的“温度”施加新的限制。这将使我们能够测试或排除像稀有中微子这样的常见暗物质候选粒子。在p3中，我们将首次测量最小的矮星不规则星系中的暗物质分布。在这样的星系中，恒星数量如此之少，以至于暗物质预计将是“原始的”，不会受到强烈恒星反馈的引力效应的影响。通过结合这些系统中气体和恒星运动的数据，我们将在迄今为止最小的尺度上测试我们的宇宙学模型，并探索暗物质的性质。在p4中，我们使用最先进的数值方法研究了银河系背景下的恒星形成和反馈。我们理解星系形成的关键瓶颈是来自巨型分子云(GMC)的恒星反馈如何与更大尺度的星系环境相耦合。在恒星形成过程中，关键的瓶颈是星系气体如何以及在何种初始状态下形成湍急的GMC。我们将首次使用“变焦”模拟来模拟恒星在其银河系环境中的形成，从而解决这两个问题。这些自古以来就为人们所知，但它们的形成机制仍然难以捉摸。它们仅仅是星团恒星形成的大质量末端吗？如果是这样的话，为什么它们在颜色、年龄、金属丰度及其空间/运动学分布上表现出如此独特的双通道？我们将使用我们最先进的星系形成模拟-解决最大质量的恒星形成区域-第一次为GC形成建立一个单一的统一模型。最后，在p6中，我们看看我们可以从附近的大麦哲伦星云中的“30 Doradus”复合体中了解到什么关于恒星形成的信息。这是许多年轻的大质量O星的家园，它们将在几百万年后以超新星的形式爆炸。这些大质量恒星的诞生地被认为是致密星团的核心。然而，其中约三分之二是在星团之外发现的。据观察，其中一些正在以极快的速度移动--即所谓的“逃逸”恒星。我们将研究大质量恒星如何以及为什么逃离它们的母星团，并考虑这对剑鱼座30内恒星形成的影响，以及对宿主星系规模的影响。

Our new group at the University of Surrey has computational and dynamical expertise over a wide range of scales from the stars orbiting around Sag A*, to cosmological simulations of the Universe. By tying these different scales together for the first time, we seek to shed new light on key outstanding problems in modern astrophysics: - How do massive black hole (BH) binaries merge? (p1); - What is the nature of dark matter? (p2; p3); - How do galaxies form? (p4); - How do globular clusters form? (p5); and - How do massive stars form? (p6) At the same time, we will build a community simulation database to: (i) provide mock data for up-coming missions eLisa, Gaia, Alma, Euclid and SKA; and (ii) to guide our theoretical understanding of these new and exciting data.In p1, we study the coalescence of supermassive BHs in galactic centres. While every massive galaxy appears to host a supermassive BH, a close binary pair of holes has never been seen. Understanding how and why such binaries merge is important for the formation and evolution of galactic bulges, and because such mergers produce gravitational waves that are visible across the entire Universe. In this project, we will study in detail the combined effect of four coalescence mechanisms - one of which is completely new - for the first time.In p2 and p3, we probe the nature of dark matter. Dark matter is an invisible substance that appears to make up most of the gravitating mass of the Universe, yet it remains mysterious. In p2, we exploit a new numerical technique for modelling dark matter fluids to place new constraints on the "temperature" of dark matter. This will allow us to test or rule-out popular dark matter particle candidates like sterile neutrinos. In p3, we will measure the dark matter distribution in the smallest dwarf irregular galaxies for the first time. In such galaxies, there are so few stars that the dark matter is expected to be "pristine", untouched by the gravitational effects of strong stellar feedback. By combining data for gas and star motions in these systems, we will test our cosmological model, and probe the nature of dark matter, on the smallest scale to date.In p4, we study star formation & feedback in a galactic context using state-of-the-art numerical methods. The key bottleneck in our understanding of galaxy formation is how stellar feedback, originating within giant molecular clouds (GMCs), couples to the larger scale galactic environment. In star formation, the key bottleneck is how, and in what initial state, turbulent GMCs form from galactic gas. We will solve both by using "zoom" simulations to model star formation in its galactic context, for the first time.In p5, we study the formation of globular clusters (GCs). These have been known about since antiquity yet their formation mechanism remains elusive. Are they simply the massive end of clustered star formation? And if so, why do they show such a distinctive bi-modality in colour, age, metallicity and their spatial/kinematic distribution? We will use our state-of-the-art galaxy formation simulations - that resolve the most massive star forming regions - to construct a single unified model for GC formation, for the first time.Finally, in p6 we look at what we can learn about star formation from the nearby "30 Doradus" complex in the Large Magellanic Cloud. This is home to many young massive O stars that will explode as supernova just a few million years from now. The birth sites of these massive stars are believed to be the cores of dense stars clusters. However, ~two thirds of them are found outside of stars clusters. Some of these are observed to be moving at great speed - so-called "runaway" stars. We will study how and why massive stars escape their parent clusters, and consider the implications of this both for star formation within 30 Doradus, and on the scale of the host galaxy.