Ubiquitous velocity fluctuations throughout the molecular interstellar medium

Jonathan Henshaw

Thursday December 3rd, 15:00

To understand the initial phases of star and planet formation we must first understand how dense, star-forming gas is assembled in galaxies. This gas determines not only where and how many stars will form, but also where they release the energy, momentum, and heavy elements that drive galaxy evolution. Density variation in interstellar gas is both created and amplified by gas motion, with the compressive motions responsible driving star and planet formation likely resulting from a combination of instabilities, convergent atomic and molecular flows, and turbulence. However, establishing which of these mechanisms dominate on different physical scales and in different galactic environments is challenging. In this contribution, I will present our recent work in which we have measured the motion of molecular gas in both the Milky Way and nearby galaxy NGC 4321; assembling observations spanning four orders of magnitude in spatial dynamic range. I will present our finding that gas motions throughout the cold ISM appear to ripple in velocity, irrespective of scale or galactic environment. These velocity fluctuations, reminiscent in appearance of waves on the surface of the ocean, represent localised gas flows. I will demonstrate how, using statistical techniques, we are able to link interstellar gas flows to their driving mechanisms, thereby paving the way towards understanding the physics of dense gas assembly during the star formation process.