ERS Science on HST WFC3 (Exceptional Responsive Standard Grant application)

丝绸项目：近几十年来，天体物理学的一个中心话题是大质量早期型（椭圆和透镜状）星系的恒星形成历史。在附近的宇宙中，早期型恒星拥有超过50%的恒星质量，考虑到它们在星系普查中的主导地位，对它们的演化进行彻底的了解是至关重要的。过去使用光学（主要是可见光）波长对早期类型进行的研究强烈暗示，它们的恒星群完全是古老的。然而，目前被接受的星系形成范式假设，早期类型的形成是在宇宙的生命周期中通过多次较小物体的合并形成的。一个明确的预测是，每次合并都会形成一些恒星，因此这些天体中的恒星数量并不完全是古老的。最近的一项重大突破是利用紫外线（UV）数据表明，早期型星系中确实存在年轻恒星，其数量与标准模型预测的大致相同。在早期型星系中对年轻恒星的明确探测是现代关于它们形成的争论的一个重要结果。提出的计划通过探索这些星系内年轻恒星的空间分布来扩展和增强这些新结果，这是至关重要的下一步，将为早期型系统中导致恒星形成的过程提供重要的见解。迪斯尼项目：星系的演化主要是气体转变成恒星。但是到目前为止，由于我们只能通过恒星的特性来寻找星系，我们可能错过了它们历史上最早的、也许是最有趣的阶段。在这个项目中，我们的目标是研究附近一个巨大的“未进化”星系，其中有不成比例的气体尚未变成恒星。这个星系是一个完美的实验室，可以用来研究原始系统，研究气体如何以及以什么速度变成恒星。该项目将探索气体密度和恒星形成活动之间的相互作用，并为星系形成过程提供重要的见解。

Silk project: Over recent decades, a central topic in astrophysics has been the star formation histories (SFHs) of massive early-type (elliptical and lenticular) galaxies. Early-types host more than 50 percent of the stellar mass in the nearby Universe and, given their dominance of the galaxy census, it is crucial to develop a thorough understanding of their evolution. Past studies of early-types using optical (mainly visible) wavelengths strongly implied that their stellar populations are exclusively old. However, the currrently accepted galaxy formation paradigm postulates that early-types form over the lifetime of the Universe through multiple mergers of smaller objects. A clear prediction is that each merger should form some stars and therefore the stellar population in these objects is not exclusively old. A major recent breakthrough has been the use of ultra-violet (UV) data to show that young stars do indeed exist in early-type galaxies, in roughly the amounts predicted by the standard model.The unambiguous detection of young stars in early-type galaxies is a significant result in the modern debate over their formation. The proposed program extends and enhances these new results by exploring the spatial distribution of young stars inside these galaxies, a crucial next step which will provide important insights into the processes that lead to star formation in early-type systems. Disney project: Galaxy evolution is largely the transmutation of gas into stars. But as we have so far been forced to find galaxies by the properties of their stars alone we have probably missed the earliest and perhaps most interesting phases in their history. In this project we aim to study a massive nearby 'underevolved' galaxy in which there is a disproportionate amount of gas that has not been turned into stars. This galaxy is a perfect laboratory for studying primordial systems and for working out how and at what rate gas is turned into stars. The project will explore the interplay between gas density and star formation activity and provide important insights into the process of galaxy formation.