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

• Applicant: Dr. Mélanie Chevance, since 8/2022
• Subject Area: Astrophysics and Astronomy
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 417450974

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.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Dr. Diederik Kruijssen, until 7/2022