Next generation hydrodynamic simulations of galaxy clusters

星系团拥有宇宙中最大的星系，其恒星质量高达太阳质量的一万亿倍。这些星系周围环绕着巨大的热x射线等离子体，温度超过1000万开尔文。然而，一个令人困惑的观察是，这些气体并没有以预期的速度冷却并形成新的恒星——为什么在大质量星系中恒星的形成会停止？目前最受欢迎的一种解释是，活跃的星系核（AGN）通过发射强大的射电明亮的相对论性等离子体射流，使气体保持高温。AGN由超大质量黑洞的吸积提供动力，在能量上能够抵消x射线气体中的辐射损失，甚至可以将一些气体完全赶出系统。星系团的现代流体动力学模拟试图包括这种所谓的AGN反馈过程的影响，并且可以成功地模拟最亮的星系团星系中恒星形成的关闭，同时产生具有观测合理质量的黑洞。然而，这些模拟目前很难重现气体的x射线热特性，预测在星系团核心中往往太热和扩散的物质。这种差异很可能是由于目前的模型没有捕捉到所有基本的物理现象，也可能是由于数值分辨率不足。在这个博士项目中，该学生将加入正在进行的合作努力，使用SWIFT流体动力学代码（SWIFT .dur.ac.uk）开发具有改进分辨率和物理建模的新一代群集模拟。他们将从事涉及分析新的模拟数据的科学项目，并有机会帮助开发和测试新的模拟模型。该学生将加入Virgo联盟并使用DiRAC高性能计算设施（DiRAC .ac.uk）。

Galaxy clusters host the most massive galaxies in the Universe, with stellar masses up to one trillion times the mass of the Sun. These galaxies are surrounded by huge reservoirs of hot, X-ray emitting plasma, with temperatures over 10 million Kelvin. A puzzling observation, however, is that this gas is not cooling down and forming new stars at the expected rate - why does star formation shut down in massive galaxies? One, currently favoured, answer is that the gas is being kept hot by an active galactic nucleus (AGN) through the emission of powerful jets of radio-bright relativistic plasma. The AGN, powered by accretion on to a super-massive black hole, is energetically capable of counteracting the radiative losses in the X-ray gas and can even drive some of the gas out of the system altogether. Modern hydrodynamic simulations of galaxy clusters attempt to include the effects of this so-called AGN feedback process and can successfully model the shut-down of star formation in brightest cluster galaxies, while producing black holes with observationally-reasonable masses. However, these simulations currently struggle to reproduce the X-ray thermal properties of the gas, predicting material that tends to be too hot and diffuse in the cluster core. Such a discrepancy is likely the result of current models not capturing all the essential physics but may also be due to insufficient numerical resolution. In this PhD project, the student will join ongoing collaborative efforts to develop a new generation of cluster simulations with improved resolution and physics modelling using the SWIFT hydrodynamics code (swift.dur.ac.uk). They will work on science projects involving the analysis of new simulation data as well as have the opportunity to help develop and test new simulation models. The student will join the Virgo consortium and use the DiRAC high performance computing facility (dirac.ac.uk).