New insight on the galaxy formation process from the star formation histories of satellite galaxies

最大的谜团之一是星系是如何聚集成我们今天看到的无数形状和大小的。我们的银河系有着迷人而复杂的结构，包括旋臂、中央的棒状和凸起、超大质量黑洞、银河喷泉和高速云。虽然银河系并不罕见，但大多数星系的质量都比银河系小几千倍；有些要大上几百倍。事实上，没有两个星系看起来是相同的，这是一个谜，因为宇宙本身在大爆炸中以非常均匀的状态出现。此外，结构的增长是由神秘的暗物质主导的，暗物质只通过引力相互作用，因此在所有尺度上都应该是相似的。对星系出现的解释在于热气体、冷气体和恒星之间复杂的相互作用。当超新星爆炸，巨大的黑洞吸积气体，分子云冷却形成新的恒星时，大量的能量在这些阶段之间交换。先进的星系形成理论为我们提供了一个很好的框架来解释我们的观测结果，但这个模型依赖于许多近似值和假设，而这些近似值和假设很少受到当前数据的约束。这项研究将集中于“卫星星系”的演化，即围绕较大星系运行的系统。对于它们所观察到的许多特征，目前还没有一个自洽的解释，人们也不明白为什么它们的演化与它们所环绕的宿主星系如此不同。进展的主要限制之一是缺乏宇宙历史早期卫星星系的良好数据。通过使用新的仪器和先进的建模技术进行雄心勃勃的观察，这项研究将使我们对这些有趣而重要的星系的理解有一个巨大的飞跃。调和现有的冲突与模型将导致对负责星系形成和演化的基本物理过程的新发现。

One of the great mysteries is how galaxies assembled into the myriad shapes and sizes we see today. Our own Milky Way has a fascinating, complex structure including spiral arms, a central bar and bulge, a supermassive black hole, Galactic fountains and high velocity clouds. And while the Milky Way is not unusual, most galaxies are thousands of times less massive; some are hundreds of times larger. In fact, no two galaxies look the same, which is something of a puzzle since the Universe itself arose out of the Big Bang in a very uniform state. Moreover, structure growth is dominated by mysterious dark matter, which interacts only via gravity and thus should look similar on all scales. The explanation for the appearance of galaxies lies in the complex interplay between hot gas, cold gas, and stars. Enormous amounts of energy are exchanged between these phases, as supernovae explode, giant black holes accrete gas, and molecular clouds cool down to form new stars. Advanced galaxy formation theory gives us a good framework with which to interpret our observations, but the model relies on many approximations and assumptions that are poorly constrained by current data. This research will focus on the evolution of "satellite galaxies", which are systems that orbit larger galaxies. There is no self-consistent explanation for many of their observed characteristics, and it is not understood why they should have evolved so differently from the host galaxy around which they orbit. One of the main limitations to progress has been the lack of good data on satellite galaxies at earlier times in the Universe's history. Through ambitious observation using new instrumentation, and advanced modeling techniques, this research will result in a monumental leap forward in our understanding of these interesting and important galaxies. Reconciling the existing conflicts with models will lead to new discoveries about the fundamental physical processes responsible for the formation and evolution of galaxies.