Title: nIFTy Galaxy Cluster simulations VI: The gaseous outskirts of galaxy cluster Show Chinese title

Title: nIFTy星系团模拟VI：星系团的气体外缘

Abstract: Galaxy cluster outskirts provide an intriguing testbed for theories of cosmic structure formation and galaxy formation, marking the transition from the mildly non-linear cosmic web to the highly non-linear, virialised, cluster environment. It is here that cluster environment begins to influence the gaseous content of galaxies, and here that we expect to find shocks in the intra-cluster medium (ICM) associated with infalling galaxy groups and gas accretion from the cosmic web. Using a suite of cosmological hydrodynamical zoom simulations of a single galaxy cluster from the nIFTy comparison project, we investigate what current state-of-the-art astrophysics codes predict for ICM structure, kinematics, and thermodynamics in cluster outskirts. These include non-radiative simulations, which probe differences in schemes for solving the equations of hydrodynamics, and full physics simulations, which probe differences in galaxy formation modeling. Our analysis reveals that the ICM in cluster outskirts is relatively insensitive to both choice of code and galaxy formation prescription. Spherically averaged gas density profiles follow the underlying dark matter, scaled by the cosmic baryon fraction, while temperature and velocity profiles show signatures of strong shocks, short-lived interior to the virial radius and longer-lived at larger radii. These shocks can be understood as the combined response to infalling gas accreted along filaments, which we demonstrate by reconstructing the local cosmic web, and along the orbits of accreted substructures. Our results make clear that cluster outskirts are shaped by large-scale gravitational dynamics and strong, inefficiently radiating, shocks. Show Chinese abstract

Abstract: 星系团边缘为宇宙结构形成和星系形成理论提供了一个引人入胜的试验场，标志着从温和非线性的宇宙网过渡到高度非线性、达到势能平衡的星系团环境。 在这里，星系团环境开始影响星系的气体含量，也是我们预期在星系团内介质（ICM）中发现与流入的星系群和来自宇宙网的气体吸积相关的激波的地方。 利用来自nIFTy比较项目的单个星系团的宇宙学流体动力学zoom模拟套件，我们研究了当前最先进的天体物理代码对星系团边缘ICM结构、运动学和热力学的预测。 这些包括非辐射模拟，用于研究求解流体力学方程的不同方案，以及全物理模拟，用于研究星系形成建模的不同差异。 我们的分析表明，星系团边缘的ICM相对不敏感于代码的选择和星系形成方案。 球对称平均气体密度剖面遵循暗物质的分布，由宇宙重子分数缩放，而温度和速度剖面显示出强烈激波的特征，这些激波在virial半径内部短暂存在，在更大半径处则持续时间更长。 这些激波可以理解为沿丝状结构吸积的气体以及被吸积次结构轨道的共同响应，我们通过重建局部宇宙网来证明这一点。 我们的结果明确表明，星系团边缘是由大尺度引力动力学和强而低效辐射的激波塑造的。