Comprehensive Model for the Formation-Evolution of Massive Cosmic Systems: The Answer is Blowing in the Wind

大质量宇宙晕是一个非凡的系统，它包括宇宙中最大质量的星系以及星系群和星系团。这些晕的质量从相当于10,000亿个太阳到令人难以置信的10亿个太阳，是宇宙中最大、质量最大的引力约束物体。它们的大部分质量是暗物质。在组成这些系统的可见物质中，大部分是百万度(或更高)热的X射线发射气体的形式。这些光晕拥有巨大的黑洞，这些黑洞以周围的气体为食，推动着延伸出10万光年或更远的强大喷流。我们今天观察到的这些系统是如何形成的？是什么过程塑造了他们？这些都是迫在眉睫的问题的一个原因是，宇宙中50%的星系都是大质量晕的宿主，在不知道其中相当一部分的演化是如何受到它们所处的极端环境影响的情况下，无法解释为什么观测到的星系表现出它们的特性。另一个原因是，巨大的晕是宇宙结构中最年轻的形成。事实上，最大质量的天体仍然带有导致它们形成的条件的印记，因此被认为是对宇宙几何和膨胀的重要探测器。然而，将星系团用作宇宙学探测器，关键取决于我们对局部宇宙中星系团为什么看起来是这样的，以及它们在早期是什么样子的理解程度。我的研究重点是开发解决上述问题的现实模型。这种模型包括在强大的超级计算机上进行最先进的计算机模拟，以“虚拟”地复制宇宙137亿年的历史，并试图在模型框架内尽可能全面地描述影响大质量光晕特征的相互关联的物理过程的令人难以置信的复杂网络。这些过程包括：(A)塑造会聚暗物质流的流动并随时间产生越来越大的宇宙结构；(B)控制星系的形成以及恒星的诞生、生死和死亡；(C)描述热气体对星系的作用，因为后者加速穿过星系；到(D)产生风，把恒星碎屑以及垂死恒星释放的爆炸能量输送出星系，进入更广泛的环境；(E)调节超大质量黑洞从其周围环境捕获和吸收气体时的反应；以及更多。数值模拟是解开这张网的唯一途径。挑战在于确保模拟正确地捕捉到所涉及的物理，而要做到这一点--在当今计算限制的限制下--需要独创性、创造力和洞察力。**

Massive cosmic halos, a category that includes the most massive galaxies in the universe as well as galaxy groups and clusters, are remarkable systems. With masses ranging from an equivalent of 10,000 billion to a mind-boggling million billion suns, these halos are the largest, most massive gravitationally bound objects in the cosmos. The majority of their mass is dark matter. Of the visible matter that comprises these systems, the bulk is in the form of million degrees (or more) hot, X-ray emitting gas. The halos host gargantuan black holes that feed off the ambient gas and propel powerful jets that extend out a hundred thousand light-years or more. How did these systems we observe today form? What processes have shaped them? One reason why these are pressing questions is that the massive halos collectively host >50% of the galaxies in the universe and it is just not possible to explain why the observed galaxies exhibit the properties they do without knowing how a significant fraction's evolution is impacted by the extreme environment they reside in. Another reason is that the massive halos are the youngest of the cosmic structures to have formed. In fact, the most massive still bear the imprints of the conditions that led to their formation and therefore, have been identified as important probes of the geometry and the expansion of the universe. The use of galaxy clusters as cosmological probes, however, depends critically on how well we understand why clusters in the local universe look the way they do, and what they looked like at an earlier epoch. My research focuses on developing realistic model that seeks to address the above issues. This modeling involves carrying out state-of-the-art computer simulations on powerful supercomputers to replicate "virtually" the universe's 13.7 billion year history and attempt to describe, as thoroughly as possible within the framework of the model, the incredibly complex web of inter-related physical processes that influence the characteristics of the massive halos. These processes range from those that (a) shape the flow of convergent dark matter flows and give rise to increasingly larger cosmic structures with time; (b) govern the formation of galaxies, and the birth, life and death of stars therein; and (c) describe the action of the hot gas on the galaxies as the latter speed through the former; to those that (d) are responsible for winds that transport stellar detritus as well as the explosive energy released by dying stars out of the galaxies and into the wider environment; (e) regulate the response of supermassive black holes as they capture and draw in gas from their surroundings; and more. Numerical simulations are the only way of unraveling this web. The challenge lies in ensuring that the simulations correctly capture the physics involved, and doing so – within the constraints imposed by today's computational limitations – requires ingenuity, creativity and insight. **