Measuring the lifecycle of 30,000 molecular clouds across the main sequence of galaxies

恒星形成和恒星反馈在星系演化中起着至关重要的作用，但人们对其潜在的物理机制知之甚少。恒星在各种各样的环境中形成，恒星形成与星系环境之间的相互作用被认为是高度复杂的。恒星形成理论试图将星系恒星的形成描述为发生在分子云内的过程的结果，但在这些小空间尺度上存在着一个关键的缺乏观测约束的问题——直到最近，这些都是无法解决的观测。我们将通过利用我们正在进行的阿塔卡马大型毫米/亚毫米阵列（ALMA）的大型项目，推动我们对恒星形成和反馈的理解取得重大进展，该项目具有前所未有的分辨率和灵敏度，可以实现对本星系外星系分子云的详细观测，从而在各种环境中实现恒星形成的统计代表性观点。我们的团队在描述恒星形成的生命周期和来自ALMA +星系光学观测的反馈方面处于世界领先地位，使用了我们内部开发的一种新的统计方法。对十几个星系的初步应用揭示了星系之间和单个星系内部恒星形成的各种云尺度条件（例如分子云寿命，恒星形成效率，碎片尺度）和施加恒星反馈（例如时间尺度，速度和恒星消散母云的效率）。主要的问题是这种变化来自哪里，以及它如何与星系环境（例如气体表面密度，星系动力学，形态）相关联。要回答这个问题，需要一个统计上具有代表性的星系样本来探测恒星形成的各种环境。我们目前正在进行的ALMA大型项目为解决这个问题提供了理想的机会，让我们能够以必要的（云尺度）分辨率访问80个恒星形成星系中的30,000个巨大分子云。我们将应用我们的新分析方法，推导上述描述云尺度恒星形成和反馈的物理量，并研究它们与银河系环境的联系。分析如此大的星系样本是一个雄心勃勃的项目，它大大扩展了我们的研究范围，需要一个专门的研究人员。它将为星系特性与云尺度恒星形成和恒星反馈之间的多尺度耦合提供明确的观测特征，这是确定驱动星系演化的物理过程的关键一步。这个项目很好地融入了我们集团和国际PHANGS合作。它得益于最先进的手头数据和经过良好测试的分析方法，这使它成为博士生的完美项目。

Star formation and stellar feedback play a critical role in galaxy evolution, but the underlying physical mechanisms are poorly understood. Stars form in a large variety of environments, and the interaction between star formation and the galactic environment is thought to be highly complex. Theories of star formation attempt to describe galactic star formation as the result of processes taking place within molecular clouds, but there exists a crucial lack of observational constraints on these small spatial scales - until recently, these were inaccessible to resolved observations.We will drive major progress in our understanding of star formation and feedback by exploiting our ongoing Large Programme on the Atacama Large Millimeter/submillimeter Array (ALMA), which has the unprecedented resolution and sensitivity needed to achieve detailed observations of molecular clouds in galaxies outside of the Local Group, enabling a statistically representative view of star formation across a wide variety of environments. Our group is world-leading in characterising the lifecycle of star formation and feedback from ALMA + optical observations of galaxies, using a new statistical method that we have developed in-house. Initial applications to a dozen galaxies reveal a great variety of cloud-scale conditions under which stars form (e.g. the molecular cloud lifetime, star formation efficiency, fragmentation scales) and exert stellar feedback (e.g. the timescales, velocities, and efficiencies with which stars dissipate their parent cloud), both between galaxies and within individual ones. The major question is where this variety comes from, and how it plausibly correlates with the galactic environment (e.g. gas surface density, galactic dynamics, morphology). Answering this question requires a statistically representative galaxy sample to probe the variety of environments in which stars formOur currently ongoing ALMA Large Programme provides the ideal opportunity to solve this problem by giving us access to 30,000 giant molecular clouds in 80 star-forming galaxies at the necessary (cloud-scale) resolution. We will apply our new analysis method, derive the above physical quantities describing cloud-scale star formation and feedback, and investigate their connection to the galactic environment. Analysing such a large galaxy sample is an ambitious project, which significantly expands the scope of our research and requires a dedicated researcher. It will provide the definitive observational characterisation of the multi-scale coupling between galaxy properties and cloud-scale star formation and stellar feedback, which is a critical step to identify the physical processes driving galaxy evolution.This project is well-embedded within our group and in the international PHANGS collaboration. It benefits from state-of-the-art in-hand data and a well-tested analysis method, which makes it a perfect project for a PhD student.