Astrophysics at the University of Bath 2020-2023

巴斯的天体物理学家研究在膨胀的宇宙中爆炸的恒星、成长的星系和喂养黑洞。我们建议将观测、理论和模拟相结合，以解决从高能和时间域天文学到星系的形成、它们与超大质量黑洞和宇宙学的共同演化等一系列不同的问题。先进的统计方法将有助于解释我们的观测和计算结果。联合起来，我们的研究问题将在最广泛的尺度上阐明我们所生活的“动态宇宙”。在最小的尺度上，与大质量恒星及其留下的致密残骸的死亡相关的高能现象可以被实时监测。来自恒星黑洞和中子星周围以及它们之间相互作用的辐射，打开了一扇无法在地球上复制的极端物理窗口。我们的团队率先对偏振光进行了测量，揭示了磁场在塑造从这些暴力事件中出现的相对论喷流中的重要性。对在电磁光谱中观察到的丰富现象的物理解释将通过最先进的模拟来实现，这些模拟能够预测所谓的光曲线，描述在X射线、光学和无线电波长上看到的快速时间变化。与以前的建模工作不同的是，将纳入关于喷流结构和动力学的重要课程，并将结合来自与光完全不同的探测器的信息，即引力波。最近在多信使天文学方面的这一突破进一步允许测试一种情景，在这种情景中，由于一个鼓舞人心的同伴引起的共振，中子星极其致密的外壳可以猛烈地粉碎。我们将设计出对这些事件的多信使信号以及它们被预期观察到的速度的严格预测，从而可以对这些超高密度天体中正在发挥作用的极端核物理做出推断。缩小到星系尺度，相关的时间尺度会同步增加。在这里，大质量恒星临终前发生的伽马射线爆发也起到了关键作用。由于它们的亮度很高，可以在很远的宇宙学距离内观察到，所以我们可以将它们作为一种独特的背景探测器，用来研究气体、恒星形成和尘埃之间的循环，这些循环支配着星系中恒星的形成。新的空间分辨光谱观测将使我们能够有意义地将这些信息与对其宿主星系的互补观测配对。类似的技术将支持一项研究，该研究将对星系的动力学和形态进行观察，以解决长期存在的争论，即星系中心超大质量黑洞的形成与星系间碰撞造成的破坏之间的联系。选择偏差将通过联合分析观测和先进的宇宙学模拟来解释。同样，将全新的观测与宇宙学模拟相结合，我们将把目光转向宇宙前沿，绘制出早期宇宙中已知的最密集结构中的星系在其演化的头30亿年期间的出现情况。我们对今天星系团祖先的普查将揭示它们对早期恒星形成的重要性，以及环境对星系演化的影响。它将进一步检验宇宙结构形成理论。在尽可能大的时空尺度上，整个宇宙随着它的加速膨胀，是一个动态系统。准确的扩张速度是一个激烈辩论的问题，不同的测量方法显然是相互矛盾的。我们对变星的实时监测有可能解决这一争论，或者揭示挑战我们标准宇宙学的基本新物理学。

Bath astrophysicists study exploding stars, growing galaxies and feeding black holes in an expanding Universe. We propose to combine observations, theory and simulations to tackle a diverse array of problems from high energy and time domain astronomy to the formation of galaxies, their co-evolution with supermassive black holes and cosmology. Advanced statistical methods will aid the interpretation of our observational and computational results. Jointly, our research questions will illuminate the 'dynamic Universe' we live in on the widest range of scales.On the smallest scales, the high energy phenomena associated with the death of massive stars and the compact remnants they leave behind can be monitored real-time. The emission coming from the immediate surroundings of stellar black holes and neutron stars, and from interactions between them, opens a window on extreme physics that cannot be replicated on Earth. Our group pioneered measurements of polarised light, revealing the importance of magnetic fields in shaping the relativistic jets emerging from these violent events. Physical interpretation of the rich phenomenology observed across the electromagnetic spectrum will be enabled by state-of-the-art simulations capable of predicting so-called light curves, describing the rapid temporal variations as seen at X-ray, optical and radio wavelengths. New compared to previous modelling efforts is that important lessons on jet structure and dynamics will be incorporated, and information from an entirely different probe than light will be tied in, namely gravitational waves. This recent breakthrough in multi-messenger astronomy further allows tests of a scenario in which the incredibly dense crust of neutron stars can violently shatter due to resonances induced by an inspiraling companion. We will devise rigorous predictions of the multi-messenger signatures of such events and the rates at which they are anticipated to be observed, allowing inferences on the extreme nuclear physics at play in these ultradense objects.Zooming out to galaxy scales, the relevant timescales increase in lockstep. Here too, gamma-ray bursts happening during the final death throes of massive stars play a key role. Since by their sheer brightness they are observable out to large cosmological distances, we can use them as a unique background probe against which to study the cycle between gas, star formation and dust that governs the build up of stars in galaxies. New spatially resolved spectroscopic observations will allow us to meaningfully pair this information with complementary observations of their host galaxies. Similar techniques will underpin a study that pairs observations of the dynamics and morphologies of galaxies to settle a long-standing debate on the connection between fuelling of supermassive black holes at the centres of galaxies and the disruptions induced by the collision between galaxies. Selection biases will be accounted for by jointly analysing observations and advanced cosmological simulations. Similarly pairing brand-new observations with cosmological simulations, we will turn our eyes to the cosmic frontier, mapping the emergence of galaxies in the most overdense structures known in the early Universe during the first 3 billion years of its evolution. Our census of the progenitors to today's galaxy clusters will reveal their importance to early star formation and the impact of environment on galaxy evolution. It will further allow a test of cosmological structure formation theory.Arriving at the largest possible spatial and temporal scales, the entire cosmos, with its accelerated expansion, is a dynamic system. The precise rate of expansion is a matter of intense debate with different measurement methodologies in apparent contradiction. Our real-time monitoring of variable stars has the potential to resolve this debate or, alternatively, reveal fundamental new physics challenging our standard cosmology.