Fakultät für Physik und Astronomie
STEPHEN PHILLIPS hostreviews.co.uk / UNSPLASH

The cloud-scale baryon cycle across the nearby galaxy population

Melanie Chevance , ARI

The cycling of matter in galaxies between molecular clouds, stars and feedback is a major driverof galaxy evolution. However, it remains a major challenge to derive a theory of how galaxies turn their gasinto stars and how stellar feedback affects the subsequent star formation on the cloud scale, as a functionof the galactic environment. Star formation in galaxies is expected to be highly dependent on the galacticstructure and dynamics, because it results from a competition between mechanisms such as gravitationalcollapse, shear, spiral arm passages, cloud-cloud collisions, and feedback processes such as supernovae, stellarwinds, photoionization and radiation pressure. A statistically representative sample of galaxies is thereforeneeded to probe the wide range of conditions under which stars form. I will present the first systematiccharacterisation of the evolutionary timeline of the giant molecular cloud (GMC) lifecycle, star-formation andfeedback in the PHANGS sample of star-forming disc galaxies. I will show that GMC are short-lived (10-30Myr) and are dispersed after about one dynamical timescale by stellar feedback, between 1 and 5 Myr aftermassive stars emerge. Although the coupling efficiency of early feedback mechanisms such as photoionisationand stellar winds is limited to a few tens of percent, it is sufficient to disperse the parent molecular cloudprior to supernova explosions. This limits the integrated star formation efficiencies of GMCs to 2 to 10 percent. These findings reveal that star formation in galaxies is fast and inefficient, and is governed by cloud-scale, environmentally-dependent, dynamical processes. These measurements constitute a fundamental testfor numerical sub-grid recipes of star-formation and feedback in simulations of galaxy formation and evolution.

ARI Institute Colloquium
16 Dec 2021, 11:15
ARI, Moenchhofstrasse 12-14, Seminarraum 1, 1.OG

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