Understanding the role of feedback from supermassive black holes in galaxy formation

宇宙结构形成和演化的冷暗物质模型成功地描述了星系和星系团如何在整个宇宙中传播。然而，它无法描述星系本身的基本性质。天文学家开始意识到，这种失败与物理学中缺失的一个关键部分有关：星系核中超大质量黑洞的物质和能量流出。这些外流很难建模，部分原因是对它们释放的能量几乎没有可靠的测量。最近对星系和星系团的x射线观测产生了最好的测量结果。美国宇航局钱德拉x射线天文台拍摄的高分辨率图像显示，在星系和星系团周围稀薄的热气体大气中存在巨大的空洞。这些空洞的直径通常为7万光年，但也可能达到70万光年（是银河系直径的7倍）。它们是由带电粒子沿磁场线以相对论速度旋转的强大射流产生的。这些喷流本身是由潜伏在星系核心的超大质量黑洞产生的，其质量相当于10亿个太阳。它们释放的能量超过太阳输出的能量的10万亿倍，足够的爆发力来驱动流出物，取代相当于10亿到1万亿个太阳的气体。这些流出物显然在星系形成过程中发挥了重要作用，因为它们限制了星系及其伴生的超大质量黑洞的大小。这项为期五年的星系和星系团研究结合了x射线、可见光、紫外线、红外线和射电望远镜，将描绘出星系及其超大质量黑洞如何形成和演化的生动画面。它还将深入研究从超大质量黑洞周围出现的强大而神秘的射电喷流的本质。

The Cold Dark Matter model for the formation and evolution of structure in the Universe successfully describes how galaxies and clusters of galaxies are spread throughout the cosmos.  However it fails to describe the basic properties of galaxies themselves.  Astronomers are beginning to realize that this failure is related to a key piece of missing physics: outflows of matter and energy from supermassive black holes in the nuclei of galaxies.  These outflows are difficult to model in part because there are few reliable measurements of the energy they release.  The best measurements have emerged from recent X-ray observations of galaxies and galaxy clusters.High resolution images taken with NASA's Chandra X-ray Observatory have revealed enormous voids in the rarefied atmospheres of hot gas surrounding galaxies and galaxy clusters.  The voids are typically 70,000 light years across, but can be up to 700,000 light years across (seven times the diameter of the Milky Way). They were created by powerful jets of charged particles gyrating along magnetic field lines at  relativistic speeds.  The jets themselves are created by supermassive black holes weighing as much as one billion Suns lurking in the nuclei of galaxies. The energy they release exceeds the power output of the Sun by up to ten trillion times, enough explosive power to drive outflows that displace between one billion and a trillion Suns worth of gas.  These outflows apparently play a fundamental role in the process of galaxy formation by limiting the sizes that galaxies and their attendant supermassive black holes can achieve.  This five year study of galaxies and clusters using a combination of X-ray, visual, ultraviolet, infrared, and radio telescopes will paint a vivid picture of how galaxies and their supermassive black holes form and evolve.  It will also delve deeply into the nature of the powerful and enigmatic radio jets emerging from the environs of supermassive black holes.