Mélanie Chevance
Heidelberg University
Understanding the multi-phase structure and physical conditions of the ISM in nearby galaxies
Nearby, star-forming galaxies offer the best laboratories to examine in detail how the interplay between stellar activity and the interstellar medium (ISM) depends on the galactic environment. I will present multi-wavelength Herschel and SOFIA observations of FIR fine structure lines and reveal the physical conditions in the ionized, neutral and molecular gas of nearby star-forming regions and galaxies. These diagnostics bring constraints to the fraction of molecular dark gas not traced by CO, the so-called “CO-dark gas”, >75% in the extreme environment of 30 Doradus in the Large Magellanic Cloud. Such a high fraction of CO-dark gas is expected to affect all observations of high-mass star-forming regions. This has important implications for the inferred star formation efficiencies in these environments, the rate at which feedback from massive stars evaporates the reservoir of molecular gas, and the extent to which the associated shielding enable ongoing star formation in other parts of the cloud complex. Zooming out, I will show how in-hand multi-wavelength observations of the nearby galaxy population allow us to characterise in detail the matter cycle in galaxies, from cloud assembly to star formation and cloud destruction by stellar feedback, and highlight that far-IR observations remain a key missing piece of this puzzle.
