Shaken or stirred ? The star formation cocktail, more than a matter of ingredients

Séminaire IPAG de Jan Orkisz (Chalmers), jeudi 11 juin 2020, 11h00, online seminar

In order to give birth to new stars, the matter of the interstellar medium has to progressively accumulate, go through denser and denser phases of ionised, atomic or molecular gas, forming clouds, clumps and cores in which eventually the pressure and density reach values high enough for nuclear fusion to occur.
During this evolution, the motions of this complex environment are driven by gravity, disrupted by stellar feedback, influenced by the heating and cooling of the gas... At all stages though, turbulence plays a key regulating role. This turbulence is compressible, magnetised, and therefore difficult to describe analytically, but it is one of the most important phenomena responsible for the low star formation efficiency observed in our Galaxy and beyond. This efficiency is directly related to the nature of the turbulence : the motions of the ISM are a mixture of compressive (curl-free) and solenoidal (divergence-free) flows, and the way these different modes are driven, and exchange energy, are crucial in understanding how, and how fast interstellar matter is converted into stars.