Galaxy Evolution in Dense Environments

在过去的二十年里，新的望远镜设备和专门的调查导致了银河系外天文学和宇宙学的巨大进步。虽然我们现在已经严格限制了许多描述我们宇宙的基本宇宙学参数，但关于星系和更大结构的形成和演化，仍然有令人兴奋的未解之谜。在我的小组中，我们对星系的演化以及星系与其宿主环境之间的联系感兴趣。局部宇宙中的许多星系并不是孤立存在的，而是聚集在称为星系群和星系团的系统中。为了探测星系群和星系团的演化，我们将结合多波长观测和最先进的模拟。星系群的性质大多是双峰的，有些星系是红色的，呈圆形，有些星系是蓝色的，正在形成恒星，呈圆盘状。有证据表明，随着时间的推移，星系从蓝色和恒星形成转变为红色和被动演化，但驱动这种演化的精确机制尚不清楚。猝灭是停止恒星形成的过程，这导致星系从蓝色转变为红色。我们将通过将观测到的星系特性与其宿主环境的特性相关联来研究猝灭，包括宿主质量、宿主动态状态以及渗透到群体和星系团中的x射线气体的特性。这一建议集中在三个具体的项目上，这对我们来说是一个令人兴奋的新方向，因为我们结合了尖端的观测和模拟来了解密集环境下的星系演化：1)用x射线、光学和无线电数据研究近处和远处的星系团，以确定在不同时期哪些猝灭机制是重要的。2)利用光学和无线电数据研究单个星系内的猝灭位置，确定不同星系群的猝灭是由内部过程还是环境过程主导。3)通过模拟研究星系演化对其主晕聚集历史的依赖性。通过观察和模拟的结合，我们可以很好地理解星系在宇宙时间的不同环境中进化的不同方式。

New telescope facilities and dedicated surveys have resulted in enormous progress in extra-galactic astronomy and cosmology over the past two decades. While we have now tightly constrained many of the fundamental cosmological parameters that describe our universe, there are still exciting unanswered questions concerning the formation and evolution of galaxies and larger structures. In my group we are interested in the evolution of galaxies and the connection between galaxies and their host environments. Many galaxies in the local universe do not live in isolation, but are clustered into systems called galaxy groups and clusters. In order to probe galaxy evolution in groups and clusters we will use a combination of multi-wavelength observations and state-of-the-art simulations. Galaxy populations are largely bimodal in their properties, with some galaxies being red and round and some galaxies being blue, star-forming, with disk-like shapes. There is evidence that over time galaxies transition from being blue and star-forming to red and passively evolving, but the precise mechanisms that drive this evolution are not well understood. Quenching is the process of shutting down star formation, which causes galaxies to transition from blue to red. We will study quenching by correlating observed galaxy properties with the properties of their host environment, including the host mass, host dynamical state, and the properties of X-ray gas that permeates groups and clusters. This proposal concentrates on three specific projects, which are an exciting new direction for us, because we combine cutting-edge observations and simulations to understand galaxy evolution in dense environments: 1) Study nearby and distant galaxy clusters with X-ray, optical and radio data to determine which quenching mechanisms are important at different epochs. 2) Using optical and radio data study the locations of quenching within individual galaxies and determine if quenching is dominated by internal or environmental processes for different galaxy populations. 3) Use simulations to study the dependence of galaxy evolution on the assembly history of their host halos. Through a combination of observations and simulations, we are ideally poised to understand the diverse ways in which galaxies evolve in different environments over cosmic time.