Interstellar Shocks

Séminaire IPAG de Antoine Gusdorf (LERMA), jeudi 14 janvier 2016 à 11h00, IPAG seminar room

In this talk, I will review the recent advances made on the understanding of interstellar shocks. The interstellar medium is an out-of-equilibrium medium, where energy is constantly injected in various forms : mechanical energy, photons, or cosmic rays. The propagation of shock waves is ubiquitous in the interstellar medium, where it represents an important part of the mechanical energy input. Interstellar shocks are generated by the birth (jets and bipolar outflows) or death (supernova and supernova remnants) of certain stars, or by the formation of molecular clouds (converging flows). These shocks are the subject of my research, that is based on the interpretation of observations with models. In the recent past, I have used a lot of telescopes like Spitzer, Herschel, ALMA, SOFIA or APEX to observe the sub-mm emission from shock regions (H2, CO, H2O, SiO, C, C+,…). I will show how the comparison of these observations with state-of-the-art shock models has allowed us to progress on numerous questions, related to the evolution of the interstellar medium : what are the processes at work in interstellar shocks, specially where they are subjected to energetic radiations (UV, X, gamma-rays) or to the impact of cosmic rays ? What kind of chemistry is triggered in shocked regions, and hence what is their contribution to the cycle of matter in the Galaxy ? What is the energetic impact and feedback of shocks on their local environment ? What is their contribution to the energetic balance of galaxies ? What are the scenarios of star formation, whether it generates or is triggered by the propagation of shocks ? What is the composition of cosmic rays, and how are they accelerated ?