Research in planetary formation, astrophysics, and cosmology at Bristol

这项提案是为了资助布里斯托尔大学地球科学和物理学院的行星形成、天体物理学、宇宙学和数据处理方面的前沿研究。这项工作的第一个要素是了解行星形成的早期阶段。关于这些过程的信息可以从我们太阳系陨石的化学成分和天文学上对所谓的过渡盘的观测中收集到。过渡盘是一种具有红外光谱的恒星，它表明在一定温度范围内有许多轨道尘埃，但恒星附近有一个无尘区域。理论表明，被这种过渡盘包围的恒星目前正在形成行星，但由于缺乏对存在的尘埃类型的了解，缺乏对尘埃如何转化为行星的精确计算，以及缺乏可以测试这些模型的详细成像，我们对行星系统形成过程中这一重要阶段的理解受到了阻碍。我们将通过观察不同种类的尘埃颗粒（由各种早期恒星的爆炸形成）是如何在我们太阳系的早期（40多亿年前）被分类，并随后聚集成落在地球上的不同类型的陨石，来开始解决这些问题。然后，我们可以利用这些信息来改进我们关于尘埃如何转化为行星的计算机模型，并更好地预测当我们使用新一代望远镜（阿塔卡马大型毫米波阵列）时我们应该看到什么，该望远镜具有观察这些圆盘的特殊能力。如果，当我们观察时，我们发现模型和数据之间有很好的一致性，这将给我们对我们的理论的信心，否则将刺激我们对行星形成的新理论的研究。第二部分的工作还是关于物体的形成，但在更大的尺度上，整个星系，星系团，以及整个宇宙。我们是英国一个大型项目的领导者，通过星系周围气体的x射线发射来寻找遥远而年轻的星系团（星系团）。在接下来的四年里，XMM轨道卫星的调查将发现数百个这样的高红移星团，通过研究它们的x射线发射和它们在微波背景辐射上投下的阴影，我们将能够测量它们的质量，从而发现更多关于引力如何将宇宙中的结构从原始弥漫气体中拉出来的信息。除了x射线外，星系团的主要指标是它们的星系数量，而星系团中星系的类型和质量的范围随着时间的推移而变化，可能是由于许多不同的物理原因。我们将提高我们对我们附近（以及当代宇宙中）人口的了解，作为与新星系团人口进行比较的参考。理论告诉我们，我们看到的星系不可能存在，除非通过某种反馈过程来减缓引力的影响，阻止气体坍缩成超大质量的物体。据推测，大部分反馈是由于星系中心超大质量黑洞发生的现象，我们将通过观察这些超大质量黑洞的强引力的x射线特征来研究这个过程（将它们与我们银河系中已知的较小的黑洞进行比较），并通过观察能量从黑洞附近通过喷流和其他流出物进入更广阔环境的过程。我们还将回顾我们可以详细研究的最遥远的星系和星系团，看看我们是否能理解形成过程的开始。这项工作的最后一部分涉及开发一套关键的计算机代码，我们和许多其他研究人员用它来检查天文数据。以TOPCAT为中心，这些代码是公开可用和流行的，但必须加以改进，以跟上不断变化的数据和计算需求。

This proposal is for a grant to cover cutting-edge research into planetary formation, astrophysics, cosmology, and data-handling at the University of Bristol in the schools of Earth Sciences and Physics.The first element of the work involves understanding the early phases of planet formation. Information on these processes can be gleaned from both the chemistry of meteorites in our own solar system and astronomically from observations of so-called transitional disks - stars with infra-red spectra that indicate much orbiting dust at a range of temperatures, but with a dust-free region close to the star. Theories suggest that stars surrounded by such transitional disks are currently forming planets, but our understanding of this important phase in the formation of planetary systems is hampered by lack of knowledge of the types of dust that are present, lack of accurate calculations on how dust is converted into planets, and lack of detailed imaging that can test those models. We will start to solve these problems by seeing how different sorts of dust grains (formed from the explosions of diverse earlier stars) were sorted early in our solar system's history, over four thousand million years ago, and subsequently aggregated into the different types of meteorites that fall to Earth. We can then use this information to improve our computer models of how the dust converts into planets, and to make better predictions of what we should see when we use a new generation telescope (the Atacama Large Millimeter Array) which has special capabilities for observing these disks. If, when we do look, we see good agreement between the models and the data, this will give us confidence in our theories or otherwise will spur work into new theories of planet formation.The second part of the work is again about the formation of objects, but on the much larger scale of whole galaxies, clumps of galaxies, and the Universe as a whole. We are UK leads for a large project to find distant and young clumps of galaxies (clusters) through the X-ray emission of the gas that lies around those galaxies. Over the next four years this survey with the orbiting XMM satellite will dicover hundreds of these high-redshift clusters, and by studing their X-ray emission and the shadows that they cast on the microwave background radiation we will be able to measure their masses and so to find out more about how gravity pulls structures in the Universe out of the original diffuse gas. The major indicator of clusters besides X-rays is their galaxy populations, and the range of types and masses of galaxies in clusters changes with time, possibly for a number of different physics reasons. We will improve our knowledge of the populations close to us (and so in the contemporary Universe) as a reference for comparisons with the populations in the new clusters. Theories tell us that the galaxies that we see cannot exist without some means of slowing the effects of gravity through some feedback process that stops gas collapsing into an over-massive object. It is conjectured that much of the feedback is due to phenomena occurring in a central supermassive black hole in galaxies, and we will study this process by looking at the X-ray signatures of strong gravity from these supermassive black holes (comparing them with the smaller holes known in our galaxy) and by looking at the processes by which energy emerges from the neighbourhoods of the black holes into their wider environments through jets and other outflows. We will also look back at the very most distant galaxies and clusters that we can study in detail, to see if we can understand the beginnings of the formation process.The final element of the work involves developing a crucial set of computer codes that we, and many other researchers, use to examine astronomical data. Centred on TOPCAT, these codes are publically-available and popular, but must be improved to keep pace with changing data and computing needs.