The role played by super massive black holes in magnetizing the circum-galactic medium

环星系介质(CGM)是星系形成和演化的关键，因为它对恒星和超大质量黑洞(SMBH)反馈过程提供了直接约束，人们普遍认为SMBH反馈过程控制着星系的整体性质(质量、大小、形态)。然而，为了捕捉这些反馈过程而设计的详细的数值流体力学模拟到目前为止还没有产生与在高红移星系周围观察到的CGM相匹配的CGM。据推测，这种失败反映了这样一个事实，即恒星的形成和恒星的反馈，以及SMBH的形成、吸积和反馈，都是在极小的亚星系尺度上发生的，这使得模拟在以合理的精度对它们进行建模同时分辨星系更大尺度的环境方面面临着巨大的挑战。由于超级拉格朗日精细化技术专门调整以提高CGM的数值分辨率，再加上精确的辐射传输方法自始至终地跟踪电离光子与气体的相互作用，我们最近开始的Nephthys宇宙变焦模拟套件已经开始补救这种情况。事实上，这种方法第一次揭示了与所观察到的特征相媲美的丰富特征。另一方面，模拟中仍然缺少重要的物理因素。特别是，磁场-被测量为与星系星际介质中的热能和湍流能量平均分配的磁场-对CGM结构的影响仍然是未知的领域。与此同时，有关这些场在塑造星系演化中所起作用的理论预测，无疑将有助于理解即将彻底改变这一领域的史无前例的深度射电数据。因此，DPhil项目包括两个阶段。首先，学生将扩展Nephthys的高分辨率宇宙模拟套件，目标是大质量星系的CGM，通过运行相应的MHD并包括SMBH吸积和反馈，建立在我们团队之前开发的最先进的算法基础上。其次，他们将在这些MHD模拟的后处理基础上开发自己的星系同步辐射模型，以期为即将到来的平方千米阵列仪器及其前体(与牛津大学以Jarvis教授为中心的射电天文观测组互动)产生现实的模拟观测数据。这项研究属于STFC的科学计划挑战A：宇宙是如何开始的，它是如何演化的？更具体地说，是次挑战A.4：第一批恒星、黑洞和星系是什么时候和如何诞生的？和答5：恒星和星系是如何进化的？

The circum-galactic medium (CGM) holds the key to galaxy formation and evolution as it provides direct constrains on the stellar and supermassive black hole (SMBH) feedback processes widely believed to regulate galaxy global properties (mass, size, morphology). Yet, detailed numerical hydrodynamics simulations designed to capture these feedback processes have so far failed to produce a CGM which matches that observed around high-redshift galaxies. Presumably this failure reflects the fact that star formation and stellar feedback, and SMBH formation, accretion and feedback, take place on extremely small, sub-galactic scales, making it a tremendous challenge for simulations to model them with reasonable accuracy whilst resolving the galaxy larger scale environment at the same time. Thanks to a super Lagrangian refinement technique specifically tuned to increase numerical resolution in the CGM, coupled to an accurate radiative transfer method to self-consistently follow the interaction of ionising photons with the gas, the NEPHTHYS suite of cosmological zoom simulations we have recently embarked upon has started to remedy the situation. Indeed, such an approach has, for the first time, revealed a richness of features in the CGM comparable to that observed. On the other hand, important physics is still missing from the simulations. In particular, the impact of magnetic fields --- which are measured to be in equipartition with thermal and turbulent energy in the interstellar medium of galaxies --- on the structure of the CGM remains uncharted territory. Meanwhile, theoretical predictions regarding the role these fields play in shaping galaxy evolution will undoubtedly be required to help make sense of the unprecedentedly deep radio data soon to revolutionize the field. The DPhil project therefore consists of two stages. At first, the student will expand the NEPHTHYS suite of high-resolution cosmological simulations targetting the CGM of massive galaxies, by running their MHD counterpart and including SMBH accretion and feedback, building upon state-of-the-art algorithms previously developed within our group. Secondly, they will develop their own model for galaxy synchrotron emission based on the post-processing of these MHD simulations, in a view to produce realistic mock observational data for the coming Square Kilometer Array instrument and its precursors (in interaction with the radio astronomy observational group at Oxford centred around Prof. Jarvis). 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?