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。通过首次将这些不同的尺度联系在一起，我们试图对现代天体物理学中的关键突出问题进行新的阐述：-大质量黑洞（BH）双星如何合并？(p1)暗物质的本质是什么？(p2; p3）; -星系是如何形成的？(p4)球状星团是如何形成的？(p5)大质量恒星是如何形成的？(p6)与此同时，我们将建立一个社区模拟数据库：（i）为即将到来的任务eLisa，Gaia，阿尔马，欧几里得和SKA提供模拟数据;（ii）指导我们对这些新的和令人兴奋的数据的理论理解。虽然每个大质量星系似乎都有一个超大质量黑洞，但从未见过一对紧密的黑洞。了解这种双星合并的方式和原因对于星系凸起的形成和演化非常重要，因为这种合并产生的引力波在整个宇宙中都可见。在这个项目中，我们将首次详细研究四种聚并机制的综合效应，其中一种是全新的。在p2和p3中，我们将探索暗物质的本质。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，但它仍然是神秘的。在P2中，我们利用一种新的数值技术来模拟暗物质流体，对暗物质的“温度”进行新的约束。这将使我们能够测试或排除流行的暗物质粒子候选者，如无菌中微子。在p3中，我们将首次测量最小矮不规则星系中的暗物质分布。在这样的星系中，恒星是如此之少，以至于暗物质被认为是“原始的”，不受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星星运动的数据，我们将测试我们的宇宙学模型，并探索暗物质的性质，在最小的尺度上到目前为止。在第4页，我们研究星星的形成和反馈在银河系中使用最先进的数值方法。我们理解星系形成的关键瓶颈是起源于巨分子云（GMC）的恒星反馈如何耦合到更大尺度的星系环境。在星星的形成过程中，关键的瓶颈是如何以及在什么样的初始状态下，湍流的GMC从星系气体中形成。我们将通过使用“变焦”模拟来解决这两个问题，第一次在银河系背景下模拟星星的形成。这些都是已知的，因为古代，但其形成机制仍然难以捉摸。它们仅仅是聚集的星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、金属丰度和空间/运动学分布上表现出如此独特的双峰？我们将使用我们最先进的星系形成模拟-解决最大质量的星星形成区域-来构建GC形成的单一统一模型，这是第一次。最后，在第6页中，我们将研究我们可以从大麦哲伦星云附近的“剑鱼座30”复合体中了解到的星星形成。这是许多年轻的大质量O型星的家园，它们将在几百万年后爆炸为超新星。这些大质量恒星的诞生地被认为是密集星团的核心。然而，它们中的三分之二是在星团之外发现的。其中一些被观察到以极高的速度移动-所谓的“失控”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系团，并考虑这对剑鱼座30内星星形成和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.