So-Star : The self-organized star formation process - Phase and morphological transitions, multi-scale mass and energy flows in the interstellar medium

The interstellar medium (ISM) is far from a homogenous atmosphere for our Galaxy. It is a turbulent, multiphase environment, with dramatic variations in temperature, density, magnetization, ionization, velocity, composition, and abundance. How matter evolves in a galaxy like the Milky Way, from diffuse and hot gas to dense and gravitationally stable structures producing stars, is not clear. In particular how energy, mass and momentum is transported from Galactic scales, through the different gas phases of the ISM and down to stellar scales, is still to be understood. This involves understanding the details of energy injection mechanisms at large scales, the interstellar mass and turbulence cascade, phase and chemical transitions, various instabilities, as well as the relative importance of gravity, stellar feedback, and cosmic-ray feedback at all scales. Because of the complex and non-linear physics involved in the evolution of matter in a galaxy like the Milky Way, it can be described as a self-organizing system where order arises from chaotic and random interactions. This field is currently the matter of intense research to investigate how exactly the gas flows from extragalactic scales down to individual stars. It plays a key role in understanding galaxy evolution in the Universe in general but also the origin of solar systems like our own.

A revolution is underway that will dramatically change our way of studying the ISM. Over the last decade, astronomy has seen a surge of precise, deep, large -area surveys across the electromagnetic spectrum, including polarization. With this wealth of information we are now able to make maps of the ISM in three dimensions, parsing out overlapping structures on the sky into discrete features. Insight on the kinematics, temperature, density structure, and magnetic field properties of the different ISM phases can be obtained by the combination of various observational tracers (21-cm hydrogen line, synchrotron emission, recombination lines, molecular lines, dust) to be confronted to numerical simulations.

The aim of this proposal is to assemble an international team of observers and theoreticians/numericists who are experts on the subject of the formation of molecular clouds where stars are born, as well as complex systems experts The selected participants will combine experts on the chemical and radiative processes that convert atomic gas into molecules, experts on numerical simulations of the dynamics of the ISM that drive the accumulation of gas to form dense clouds, observers that specialize in the detection of all gas phases and dust in the ISM, experts on the high-energy particles (cosmic rays) that pervade, heat and ionize the ISM, data scientists to explore new ways of analysing data and simulations, and theoreticians in the field of complex and self-organized systems.