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

点击翻译按钮获取中文摘要

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.