ASTUnderstanding cosmological probes: constraining the progenitors and diversity of Type Ia supernovae

关于我们的宇宙存在的一个基本问题是，我们现在知道的占宇宙质能70%以上的“暗能量”是什么？在上个世纪末通过测量遥远的爆炸恒星发现了这个神秘的量，这是完全出乎意料的。在那之前，人们一直认为宇宙的膨胀会由于引力而减慢，但事实上它正在加速，这引发了“暗能量”的存在，它正在对抗引力，将宇宙推开！关于暗能量的起源有许多理论预测（爱因斯坦的“宇宙常数”？新的奇异物理学广义相对论（General Relativity）但目前的测量还不能区分它们。2迄今为止，对暗能量起源最成功、最成熟的探测是对遥远的爆炸恒星（超新星）的测量。2011年诺贝尔物理学奖授予了两个团队，他们测量了遥远的超新星并发现了加速的宇宙。目前和未来最先进的望远镜和巡天望远镜（如暗能量巡天、欧洲航天局使命、欧几里得和大型综合巡天望远镜）正在设计中，以利用更大的超新星样本来限制暗能量理论。然而，为了区分这些暗能量理论，理解超新星本身也非常重要。这是我的欧内斯特·卢瑟福研究计划的目标，我将通过对Ia型超新星的观测来实现这一目标。Ia型超新星是双星系统中吸积白色矮星（小而致密的恒星）的发光恒星死亡。我将研究，是否有一种以上的方法来制造Ia型超新星？它们是怎么爆炸的？以及它们爆炸所在的星系的性质如何影响它们的性质？“我将分析来自许多望远镜的数据，包括世界上最大的望远镜之一，位于智利的欧洲南方天文台甚大望远镜（VLT），以了解是否有不止一种方式爆炸星星并产生Ia型超新星。我将使用先进的分析技术对这些数据，与英国领先的超新星理论家合作，以揭示这些恒星究竟是如何爆炸的。这将使我们能够改进当前和未来的超新星样本，以改进暗能量测量。我还将研究超新星爆炸所在的遥远星系的性质。Ia型超新星可以发生在许多不同类型的星系中，从像我们银河系这样的螺旋星系到即使用最强大的望远镜也几乎看不到的小矮星系。我将研究超新星的性质，如亮度，不同原子元素的存在和释放的能量如何取决于它们爆炸的星系的性质。我以前已经表明，Ia型超新星的性质变化取决于其宿主星系中存在的重元素的数量。现在，重要的是要了解这种多样性的原因，以及它在整个宇宙中可能如何变化。如果Ia型超新星在宇宙中不同的距离看起来非常不同，这将影响对它们进行的暗能量测量。作为欧内斯特·卢瑟福的研究员，我将处于独特的地位，通过显着提高我们对超新星Ia物理学和宇宙学的理解，从过去对暗能量的测量中取得进展。我将利用我在这一领域的丰富经验，帮助未来的调查揭示这个神秘的量是什么，它占我们宇宙的70%以上。

One of the fundamental questions that exists about our Universe is what is this 'dark energy' that we now know makes up greater than 70% of the mass-energy of the Universe? The discovery of this mysterious quantity at the end of the last century from measurements of distant exploding stars was completely unexpected. Until then, it was assumed that the expansion of the Universe would be slowing down due to gravitational attraction but instead it was found to be accelerating, invoking the presence of 'dark energy' that is acting against gravity to push the Universe apart! There are many theoretical predictions for the origin of dark energy (Einstein's 'cosmological constant'? new exotic physics? alterations to general relativity?) but current measurements cannot yet distinguish between them.The most successful and mature probe of the origin of dark energy to date is measurements of distant exploding stars (supernovae). The 2011 Nobel Prize in Physics was awarded to two groups who made measurements of distant supernovae and discovered the accelerating Universe. Current and future state-of-the-art telescopes and surveys (e.g. Dark Energy Survey, the European Space Agency mission, Euclid and the Large Synoptic Survey Telescope) are being designed to constrain theories of dark energy using larger supernova samples. However, to distinguish between these theories of dark energy, it is also very important to understand the supernovae themselves. This is the aim of my Ernest Rutherford research proposal.I will do this using observations of Type Ia supernovae, which are the luminous stellar deaths of accreting white dwarfs (small, dense stars) in binary systems. I will investigate, 'is there more than one way to make a Type Ia supernovae?', 'how do they explode?' and 'how do the properties of the galaxies within which they explode affect their properties?'I will analyse data coming from many telescopes, including one of the world's largest telescopes, the European Southern Observatory's Very Large Telescope (VLT) in Chile, to understand if there is more than one way to explode a star and produce a Type Ia supernova. I will use advanced analysis techniques on these data, in collaboration with the UK's leading supernova theorists to uncover how exactly these stars explode. This will allow us to refine current and future supernova samples to make improved dark-energy measurements.I will also investigate the properties of the distant galaxies in which the supernovae explode. Type Ia supernovae can occur in many different types of galaxies, from spiral galaxies like our Milky Way to small dwarf galaxies that are barely visible with even the most powerful telescopes. I will investigate how the properties of the supernovae such as brightness, the presence of different atomic elements and the energy released depend on the properties of the galaxy within which they explode. I have previously shown that the properties of Type Ia supernovae change depending on the amount of heavy elements present in their host galaxies. Now it is important to understand the cause of this diversity and how it might vary throughout the Universe. If Type Ia supernovae look very different at different distances in the Universe this would affect the dark-energy measurements made with them. As an Ernest Rutherford fellow, I will be in the unique position to progress from past measurements of dark energy, by significantly improving our understanding of SN Ia physics and cosmology. I will build on my extensive experience in this field and help future surveys reveal what is this mysterious quantity that makes up greater than 70% of our Universe.