Quenching star formation via hierarchical clustering of galaxies

我们周围的宇宙结构令人眼花缭乱，是天文学中最大的谜团之一。 一个宇宙是如何开始的，如此简单，平稳分布的氢气，产生了如此广泛的形状，大小和年龄的星系，排列在一个复杂的网络状结构中？ 更令人费解的是，一些未知的因素一直在阻止恒星和星系的形成。这种机制不可能在任何地方或任何时候都同样有效，才能产生我们今天看到的各种星系。 随着时间的推移，星系聚集在一起形成群体，越来越多的证据表明，正是在这个群体环境中，星系经历了深刻的变化，使它们无法形成新的恒星。 我的研究旨在提高我们对这些研究不足的系统的理解，以帮助识别和量化我们知道必须存在的有趣的天体物理学。 通过仔细的观察和理论建模，我希望能够确定星星形成活动在群体中关闭的时间尺度，以及这可能如何取决于群体质量或周围环境。 由于星系群是当今最常见的环境，而且它们的丰度随时间变化很大，这项研究的结果将对我们理解星系的形成和演化产生深远的影响。

The bewildering variety of structure in the Universe around us today is one of the biggest mysteries in astronomy. How did a Universe that started off so simply, as smoothly distributed hydrogen gas, produce galaxies with such a wide range of shapes, sizes and ages, arranged in a complex, web-like structure? More specifically puzzling is the fact that some unknown agent has been acting to prevent stars and galaxies from forming. This mechanism must not be equally efficient everywhere, or at all times, in order to give rise to the variety of galaxies we see today. As time goes on, galaxies gather together into groups, and evidence is mounting that it is within this group environment that galaxies undergo the profound change that renders them unable to form new stars. My research is aimed at improving our understanding of these poorly studied systems, to help identify and quantify the interesting astrophysics that we know must be present. Through careful observations and theoretical modeling I expect to be able to characterise the timescale over which star formation activity is shut off in groups, and how this might depend on the group mass or surrounding environment. As galaxy groups are the most common environment today, and as their abundance changes greatly with time, the results of this research will have profound consequences for our understanding of galaxy formation and evolution in general.