Nottingham Astronomy Rolling Grant 2011 - 2016

诺丁汉大学物理与天文学院的天文学研究主要集中在研究星系的形成和演化。这些由恒星、气体、尘埃和暗物质组成的引力集合是宇宙中最美丽的物体之一，现代天文学的一个主要主题是试图了解它们是如何存在的。为了解决这个复杂的问题，我们将利用我们所掌握的各种工具，包括从大规模数值模拟到使用地面和空间观测站对单个星系进行详细的观测研究。一个关键问题是星系一旦形成，如何随着时间的推移改变它们的外观。例如，我们正在研究螺旋星系如何变成毫无特征的透镜状系统，试图了解抑制它们的星星形成并消除它们的旋臂的物理过程。同样，我们正在探索许多螺旋系统中心壮观的酒吧特征出现和消失的过程，以及这些变化对周围星系的影响。我们正在研究可以改变星系外观的内部和环境过程，以获得星系转变如何发生的综合图像。我们的工作将结合联合收割机对附近系统的详细研究，寻找它们是如何形成的考古线索，并直接观察宇宙历史上过去70亿年中发生的进化。这些对星系转变的研究得到了对更遥远系统的观测的补充，这些系统捕获了星系的初始形成。在这些早期阶段，主要的谜题仍然没有解决，例如在大质量星系中终止恒星形成的机制。我们正以双管齐下的方法处理这些问题。首先，前所未有的灵敏度调查使我们能够确定星系演化对外部因素的依赖性，例如局部环境或周围暗物质晕的质量。其次，利用哈勃太空望远镜和大型地面望远镜上的新仪器进行研究，可以详细剖析各个星系在其生命开始时的结构特性。然而，仅研究可见光和近红外光并不能提供完整的图像。星系发出的能量大约有一半被星际尘埃吸收，掩盖了它们的真实结构。研究这种“偷来的星光”，它在远红外线中重新辐射，揭示了星系演化的隐藏面。到目前为止，还不可能理解这个故事的重要元素，因为我们还没有能够获得远红外观测，以重新捕获天空中有代表性的区域的这种丢失的光。2009年发射的赫歇尔空间天文台现在使我们能够获得必要的数据。我们在其中发挥主导作用的ATLAS调查是Herschel将进行的最广泛的区域调查，并将在未来许多年内远远超过这一部分频谱中的任何其他地面或空间调查。它将为分布在宇宙历史大部分时间里的约20万个星系提供尘埃含量和模糊的星星形成过程，揭示星系演化这一隐藏方面的秘密。这项研究方案的最后一个方面涉及利用该大学的超级计算设施模拟周围宇宙的整个宇宙学背景下星系的形成。通过将这种模拟的结果与广泛的观测计划进行比较，我们将能够检查我们对驱动星系演化的物理过程的理解。我们还将使用最早时期的观测结果来设置模拟的初始条件，看看我们是否可以跟踪星系到今天的后续演化。

Astronomical research in the School of Physics & Astronomy at the University of Nottingham is focused on studying the formation and evolution of galaxies. These gravitationally-bound collections of stars, gas, dust and dark matter are some of the most beautiful objects in the Universe, and a major theme in modern astronomy involves trying to understand how they came into existence. To tackle this complex question, we will draw on the full range of tools at our disposal, involving everything from large-scale numerical simulations to detailed observational studies of individual galaxies using ground- and space-based observatories. One key issue is how galaxies, once formed, alter their appearance over time. For example, we are studying how spiral galaxies can turn into featureless lenticular systems, seeking to understand the physical process that quenches their star formation and erases their spiral arms. Similarly, we are exploring the processes by which the spectacular bar features at the centres of many spiral systems can appear and disappear, and what effect these changes have on the surrounding galaxy. We are investigating both internal and environmental processes that can change the appearance of a galaxy, to obtain an integrated picture of how galaxy transformations occur. Our work will combine detailed studies of nearby systems, searching for archaeological clues as to how they were made, and direct observations of evolution taking place over the last seven billion years in the history of the Universe. These studies of galaxies in transformation are complemented by observations of even more distant systems, which capture galaxies in the act of initial formation. Major puzzles remain unresolved at these early stages, such as the mechanism responsible for terminating star-formation in massive galaxies. We are tackling these problems with a two-pronged approach. First, surveys of unprecedented sensitivity allow us to determine the dependence of galaxy evolution on external factors, such as the local environment or the mass of the surrounding dark matter halo. Second, studies using the new instruments on the Hubble Space Telescope and on large ground-based telescopes allow the structural properties of individual galaxies near the beginnings of their lives to be dissected in detail. However, studying only visible and near-infrared light cannot provide a complete picture. About half the energy emitted by galaxies is absorbed by interstellar dust, concealing their true structure. Studying this 'stolen starlight,' which is re-radiated in the far infrared, reveals this hidden side of galaxy evolution. To-date, it has been impossible to understand this vital element of the story, as we have not been able to obtain the far-infrared observations that would recapture this lost light over a representative area of the sky. The Herschel Space Observatory, launched in 2009, now allows us to obtain the necessary data. The ATLAS survey, in which we are playing a leading role, is the widest area survey that Herschel will conduct, and will far surpass any other ground- or space-based survey in this part of the spectrum for many years to come. It will characterise the dust content and obscured star formation for ~200,000 galaxies spread over most of cosmic history, revealing the secrets of this hidden aspect of galaxy evolution. The final aspect to this research programme involves using the University's supercomputing facilities to simulate the formation of galaxies in the full cosmological context of the surrounding Universe. By comparing the results of such simulations with the extensive observational programmes, we will be able to check our understanding of the physical processes driving galaxy evolution. We will also use the observations of the earliest epochs to set the initial conditions for our simulations, to see whether we can follow galaxies' subsequent evolution to the present-day.