Star Formation at the Crossroads of Gravity and Turbulence

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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.