Modelling the most extreme high redshift galaxies: from star formation rates to supermassive black hole growth

非常明亮的超红和亚微米星系（（U）LIRGS和SMG）经常被探测到，其星星形成速率超过每年100 - 1000个太阳质量，具有中等和高红移（z> 1）。形态学研究表明，这些星系似乎是合并/相互作用系统和盘星系的混合体。通过冷流的连续气体吸积也被用作在相当长的时间内维持其升高的星星形成速率的手段。此外，这些星系被认为是宇宙中最大质量的超大质量黑洞（SMBH）的宿主，此时它们输入到环星系介质（所谓的活动星系核（AGN）反馈）的能量是最大的。然而，这些物体已经证明是非常具有挑战性的模型，因为它们在本地宇宙中非常罕见，因此需要运行非常大的体积宇宙学模拟，同时仍然解决星系的星际介质（ISM）和围绕其SMBH的中心区域。越来越多的证据表明，宇宙射线和磁场在具有极端星星形成率的星系中扮演着重要角色，这使得建模更具挑战性。为了克服这些困难，这个DPhil项目建议从一个千兆秒差距的立方体暗物质模拟中提取一个罕见物体的样本，并以足够精细的空间分辨率重新模拟它们，以解决在ISM中形成的巨大分子云，包括宇宙射线和磁场。通过这一系列的模拟，学生将探索（i）高红移极端星星形成星系的环境历史以及不同反馈机制之间的相互作用（恒星风，超新星，活动星系核，可能由宇宙射线驱动的星系风）影响它们的星星形成率，（ii）模拟极端星系的ISM特性是否与观测到的一致，特别是（iii）能量如何在热/湍流/磁/宇宙射线能量之间分配，以及这是否调节星星的形成。为此，我们将特别关注外流，特别是我们将寻求确定它们的动力源（恒星或活动星系核反馈）和化学成分（热电离或冷分子气体）。这项研究福尔斯属于STFC的科学方案挑战A："宇宙是如何开始的，它是如何演变的？”，更具体地说，子挑战A.4：“第一颗恒星、黑洞和星系是何时以及如何诞生的？和A.5："恒星和星系是如何演化的？".

Extremely luminous InfraRed and SubMm galaxies ((U)LIRGS and SMGs) are routinely detected with star formation rates in excess of 100 - 1000 solar masses per year at intermediate and high redshift (z>1). Morphological studies have shown that these galaxies appear to be a mix of merging/interacting systems and disk galaxies. Continuous gas accretion via cold streams has also been invoked as a means to sustain their elevated star formation rates over significantly long periods of time. Furthermore these galaxies are thought to host some of the most massive supermassive blackholes (SMBH) in the Universe, at a time when their energy input into the circum-galactic medium (so called Active Galactic Nuclei (AGN) feedback) is the largest. However, these objects have proven notoriously challenging to model, as they are very rare in the local Universe and hence necessitate running very large volume cosmological simulations whilst still resolving the interstellar medium (ISM) of the galaxy and the central region surrounding their SMBH. Making the modelling even more challenging is increasing evidence that cosmic rays and magnetic fields are strong players in galaxies with extreme star formation rates. To overcome these difficulties, this DPhil project proposes to extract a sample of rare objects from a gigaparsec cube dark matter only simulation and re-simulate them with spatial resolution fine enough to resolve the giant molecular clouds that form in their ISM, including cosmic rays and magnetic fields. Armed with this series of simulations the student will explore (i) how the environmental history of high redshift extreme star forming galaxies and the interaction between the different feedback mechanisms (stellar winds, supernovae, AGN, galactic winds possibly powered by cosmic rays) impact their star formation rates, (ii) whether ISM properties of simulated extreme galaxies match observed ones, and especially (iii) how energy is apportioned between thermal/turbulent/magnetic/cosmic ray energies and whether this regulates star formation. For this purpose, special attention will be given to outflows, in particular we will seek to determine their powering source (stellar or AGN feedback) and chemical composition (hot ionised or cold molecular gas). Comparison to spatially resolved kinematic observations will be carried out through emission line diagnostics.This research falls within STFC's science programme challenge A: "How did the Universe begin and how it is evolving?", and more specifically sub-challenges A.4: "When and how were the first stars, black holes and galaxies born?" and A.5: "How do stars and galaxies evolve?".