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Astro Seminar

Star Formation Down to the Cloud Scale

Speaker: Thomas Williams (University of Oxford)
Date: Wednesday 25 January 2023
Time: 14:00
Venue: N3.28/Zoom

Where and how stars form within galaxies are two of the most critical questions in galaxy evolution. Our understanding of the star formation process is limited, ultimately, by our understanding of the sites of individual star formation — giant molecular clouds (GMCs). These dense, gaseous structures have sizes of 10s of pc, so the high spatial resolution required to resolve them has been mostly unattainable beyond the Local Group before the advent of the ALMA interferometer. Even then, acquiring the statistical sample of these ‘cloud-scale’ observations to answer questions like how local environment (bars, rings, etc.) module the star formation process has been an undertaking requiring 100s of hours of observing time with large teams. I will present work from the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) surveys studying where stars form, including some new results from the JWST. In these star-forming galaxies, the star formation process appears to proceed relatively homogeneously across the galaxy, with spiral arms acting simply to collect the gas, rather than enhance the efficiency of star formation. Optical interferometry from the MUSE IFU allows us to localise chemical enrichment, and I will show that more evolved and actively star forming galaxies tend to have more homogeneous metal distributions, but this appears to not be affected by local processes such as gas turbulence. Finally, I will show some ongoing results from the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM) project looking at the properties of molecular clouds in ‘red and dead’ early-type galaxies, attempting to understand why these often molecular gas-rich galaxies do not form stars. We find that the molecular gas in these galaxies is often not in virial equlibrium, and external forces such as shear are likely destroying the clouds on shorter timescales than required for star formation to occur.