Using Cosmic Beasts to Uncover the Nature of Dark Matter

暗物质的本质是现代物理学中最难以捉摸的问题。宇宙中只有5%的质量是由标准模型粒子组成的。剩下的95%将由“暗物质”和“暗能量”组成。它们是看不见的，而且大多数粒子物理理论预测暗物质与标准模型粒子的相互作用非常弱，以至于在地面实验中基本上无法检测到。如果这些理论是正确的，那么暗物质只能在它聚集到足够多的地方进行研究，因为它的引力会影响到周围我们能看到的东西。我建议追踪星系团（宇宙中质量最大的结构，也被称为“宇宙野兽”）中暗物质的行为，以区分三种主要模型：冷暗物质、热暗物质和自相互作用暗物质。我的提议利用了最近世界上最大的望远镜对星系团的观测急剧增加，这反映出该领域被认为是最优先的目标。我获得了哈勃太空望远镜最大类别项目（bbb100轨道）的观测时间，以获得有史以来最深入的星团周围图像，以及地球上最大的望远镜（VLT）的后续光谱。我设计了这些观测结果，通过“引力透镜”的作用来绘制星系团的暗物质图，引力透镜会扭曲和放大星系团后面的物体。我将使用这些数据(I)自己，（ii）校准授予主办机构的最大（但浅）哈勃成像，（iii）为欧几里得，雅典娜和詹姆斯韦伯太空望远镜等设施设定议程，并在2020年代优化设施。宇宙学模拟表明，星系团是区分暗物质模型的最佳实验室，因为它们仍在增长。集群通过相互融合而成长；每一次合并都像一个巨大的粒子对撞机。暗物质的性质是通过碰撞的轨迹揭示出来的，碰撞应该发生在恒星和（氢）气体之间。恒星和氢的特性已经被很好地理解了，所以它们就像温度计在0摄氏度和100摄氏度的校准点一样，对暗物质进行了测量。传统的研究项目通常将暗物质、恒星和气体的测量分开，因为它们需要不同的望远镜（红外线、紫外线、x射线）进行观测。我已经开发了一种多波长分析，使以前不可能的测量成为可能，比如暗物质和气体进入星系团的时间尺度，星系团达到平衡的速度，以及对可能的暗物质粒子相互作用的限制。我还领导建立了一个新的研究领域，我将在FLF期间扩大这个研究领域。当一个星系团后面发生短暂的事件（比如超新星爆炸）时，爆炸发出的光可以被引力透镜折射，沿着一条以上的视线可见。测量超新星多重成像版本之间的时间延迟可以提高绘制星系团暗物质的分辨率。此外，预测时间延迟是天体物理学中罕见的、宝贵的场合之一，在这种场合中，假设可以在几年的时间尺度内经受真正的波普尔检验。我有意安排了我的HST和VLT观测，以便发现和监测瞬态事件。它们还提供了（高风险/高回报）发现电磁对应物透镜引力波事件的可能性。因此，我的UKRI FLF研究计划将利用来自世界一流设施的最新多波长数据。它使用我的高精度技术来分析大数据，并将在达勒姆大学最先进的宇宙模拟的世界领先的理论框架内进行解释。

The nature of dark matter is the most elusive question in modern physics. Only 5% of the Universe by weight consists of standard model particles. The remaining 95% would be composed of 'Dark Matter' and 'Dark Energy'. These are invisible, and most particle physics theories predict dark matter to interact so weakly with standard model particles that it will remain fundamentally undetectable in terrestrial experiments. If these theories are correct, dark matter can only be studied where it gathers in sufficient quantities for its gravity to affect things around it we can see. I propose to track the behaviour of dark matter in galaxy clusters (the most massive structures in the universe, also called 'cosmic beasts'), to distinguish between the 3 leading models: cold, warm and self-interacting dark matter.My proposal exploits a dramatic recent increase in observations of galaxy clusters by the world's biggest telescopes, reflecting the field's recognition as a top priority goal. I have been awarded observing time on the Hubble Space Telescope in the largest category of programme (>100 orbits) to obtain the deepest ever imaging of clusters' surroundings, plus follow-up spectroscopy from the largest telescope on Earth (VLT). I designed these observations to map clusters' dark matter, via the effect of 'gravitational lensing', which distorts and magnifies objects behind the cluster. I will use these data (i) by themselves, (ii) to calibrate the largest (but shallow) Hubble imaging awarded to the host institute (iii) to set the agenda for, and optimise facilities like Euclid, Athena and the James Webb Space Telescope through the 2020s.Cosmological simulations indicate that galaxy clusters are the best laboratories to distinguish between models of dark matter, because they are still growing. Clusters grow by merging with each other; every merger acts like a gigantic particle collider. The properties of dark matter are revealed by its trajectory through a collision, which should be between that of stars and of (hydrogen) gas. The properties of stars and hydrogen are well understood, so they bookend measurements of dark matter like the calibration points on a thermometer at 0C and 100C. Traditional research programmes usually separate measurements of dark matter, stars and gas, because they require observations from different (infrared, ultraviolet, X-ray) telescopes. I have developed a multiwavelength analysis, to enable previously impossible measurements such as the time-scale on which dark matter and gas is funneled into clusters, how quickly clusters reach equilibrium, and constraints on possible dark matter particle interactions.I have also led the establishment of a new research area, which I will expand during the FLF. When transient events (such as supernova explosions) happen behind a galaxy cluster, light from the explosion can be gravitationally lensed and visible along more than one line of sight. Measuring the time delay between multiply-imaged versions of a supernova increases the resolution with which the cluster's dark matter can be mapped. Furthermore, predicting the time delay is one of those rare, precious occasions in astrophysics where a hypothesis can be subjected to a true Popperian test, within the timescale of a few years. I have intentionally scheduled my HST and VLT observations to enable the discovery and monitoring of transient events. They also offer the (high risk/high reward) possibility of discovering electromagnetic counterparts to lensed gravitational wave events.My UKRI FLF research programme will thus exploit the latest multiwavelength data from world-class facilities. It uses my high-precision techniques to analyse big data, and will be interpreted within the world-leading theoretical framework of Durham's state-of-the-art cosmological simulations.