Star Formation at the Crossroads of Gravity and Turbulence

我的研究小组正在研究有关恒星形成过程的公开问题。恒星形成是控制星系演化的主要因素之一。它定义了恒星群体，包括他们组成星团的组织和行星系统的起源。尽管发挥了核心作用，但这一过程的控制物理学尚不清楚。理论认为，重要的物理学是引力、磁力和湍流的组合，但哪种效应占主导地位，以及在什么尺度上仍存在争议。 我的团队使用大型调查和新颖的分析方法相结合来回答这些问题。测量很重要，因为恒星形成过程具有很大的随机波动和时间变异性。只有通过对主持这一过程的气体进行广泛的普查，我们才能分离出偶然性存在时的物理影响。大型调查需要自动分析方法，所以我的团队在过去五年里一直在创建和发布使这种方法成为可能的软件工具。我们现在准备将新的分析工具应用于研究恒星形成过程中三个关键尺度的最佳现场调查。 在最小的尺度上，我们正在识别引力触发分子云坍塌形成恒星的位置。我们将使用新的氨排放地图来理解这次崩塌。我们还将在我们的新分子气体目录中研究湍流的性质。我们将直接测量湍流性质的变化或磁场是否控制了气体形成恒星的效率。 接下来，我们将以附近的M33星系为实验室，研究星系盘与分子云形成之间的联系。作为距离最近的低倾角盘状星系，M33是银河系研究和对更广泛星系群体的观测之间的桥梁。使用我们从超大型阵列进行的调查，我们能够直接测量所有被认为推动分子云形成的物理过程的相对重要性。我们还将使用哈勃太空望远镜对M33进行的一项新调查的数据来测量分子云的寿命。 在最大的尺度上，我们试图理解分子云的集体行为如何产生恒星形成定律，这是一种将恒星形成率与当地星系属性联系起来的经验关系。利用我们银河系中的一颗大质量云，我们将对我们在其他星系中看到的典型恒星形成事件中的不同物理条件进行普查。我们还将使用毫米波干涉仪和光学光谱学的新数据来研究分子气体与附近20个星系的星系环境之间的联系。通过了解分子云的结构如何变化，我们就可以确定当地银河环境和恒星形成定律之间的联系。

My research group is studying open questions about the process of star formation. Star formation is one of the major agents that controls the evolution of galaxies. It defines stellar populations, including their organization into clusters and the origins of planetary systems. Despite this central role, the controlling physics for the process is unclear. Theory holds that the important physics is a combination of gravitation, magnetism, and turbulence, but which effects are dominant and on what scales remains open to debate. My group uses the combination of large surveys and novel analysis methods to answer these questions. Surveys are important because the star formation process has large random fluctuations and time variability. Only through a broad census of the gas that hosts the process can we isolate the physical effects in the presence of happenstance. Large surveys require automated analysis methods, so my group has spent the past five years creating and releasing the software tools that make this approach possible. We are now poised to bring new analysis tools to bear on best-in-field surveys that study three critical scales in the star formation process. On the smallest scales, we are identifying where gravity triggers collapse in molecular clouds to form stars. We will use new maps of ammonia emission to understand this collapse. We will also study the properties of turbulence in our new molecular gas catalog. We will directly measure if changing the turbulent properties or magnetic field control the efficiency with which gas can form stars. Next, we will study the connections between galaxy disks and the formation of molecular clouds using the nearby galaxy M33 as a laboratory. As the nearest, low-inclination disk galaxy, M33 is a bridge between Milky Way studies and observations of the broader galaxy population. Using our survey from the Very Large Array, we are able to directly measure the relative importance of all the physical processes thought to drive molecular cloud formation. We will also use data from a new survey of M33 by the Hubble Space Telescope to measure the lifespan of molecular clouds. At the largest scales, we are trying to understand how the collective behaviour of molecular clouds produces the Star Formation Law, an empirical relationship that relates star formation rate to local galaxy properties. Using a single, massive cloud in our own Galaxy, we will conduct a census of the different physical conditions in the typical star formation events we see in other galaxies. We will also use new data from millimetre-wave interferometers and optical spectroscopy to study the link between molecular gas and the galactic environment in 20 nearby galaxies. With knowledge of how the structure of the molecular clouds change, we can then identify the connection between the local galactic environment and the Star Formation Law.