Galaxy evolution in the distant universe

星系团非常像一个银河系城市--一个真正的城市环境，在这个环境中，星系在非星系团(标记为“场”)的位置上以比农村对应星系高得多的密度共存。星系团提出了许多令人费解的问题：它们是如何随着时间的推移变得更大的？通过寻找遥远的星系团，我们能直接观察到它们的增长吗？此外，丰富的星系团的核心是如何被明亮的红色椭圆星系群(而不是蓝色的富含螺旋的区域)所主导的？ 我是一个庞大的国际研究团队的一员，他们正在使用XMM-牛顿空间天文台识别新的星系团。XMM凭借其令人难以置信的明亮X射线发射来探测星系团，并揭示了一个与我们肉眼所看到的夜空非常不同的奇怪的、新的宇宙。我正在领导发现已知的最遥远星系团的努力--其中一些星系团发出的光需要超过宇宙一半的年龄才能到达我们身边。星系团的每一张图像都像是遥远过去的快照，通过比较年轻星系团的“婴儿照片”，我们可以了解塑造它们的物理原理。与我的研究生和国际合作者一起，我们有幸直接看到这些伟大的银河系城市正在建设的时代。

A galaxy cluster is very much like a galaxy city - a true urban environment where galaxies co-exist at much higher density than their rural counterparts in non-cluster (labelled "field") locations. Galaxy clusters pose a number of puzzling questions: how have they grown more massive with time and by searching for distant clusters can we observe their growth directly? In addition, how have the cores of rich galaxy clusters come to be dominated by populations of bright, red elliptical galaxies (as opposed to the blue, spiral-rich field)? I am part of a large, international team of researchers who are identifying new galaxy clusters using the XMM-Newton space observatory. XMM detects galaxy clusters by virtue of their incredibly bright X-ray emission and reveals a strange, new Universe very different to our naked eye view of the night sky. I am leading the effort to discover the most distant galaxy clusters known - the light from some of which has taken over half the age of the Universe to reach us. Each image of a galaxy cluster is like a snapshot of the distant past and by comparing the "baby photos" of young galaxy clusters we can learn about the physics that shaped them. Together with my graduate students and my international collaborators we are privileged to have a direct view back to the time when these great galaxy-cities were under construction.