Pierre Guillard is an associate Professor at Sorbonne University, and researcher at the Institut
d’Astrophysique de Paris (IAP), France. His background expertise is the physics of the interstellar medium and multi-wavelength observations of galaxy interactions and radio galaxies. He is interested in galaxy formation processes and more specifically in the role of the turbulence in the context of galaxy evolution. He is also deeply involved in the technical and science preparation of the James Webb Space telescope and Euclid missions.
Talk Title and Abstract:
Observations and modelling of signatures of the dissipation of turbulence driven by accretion, merging and feedback
The build-up of galaxies is regulated by a complex interplay between gravitational collapse, galaxy merging and feedback related to AGN and star formation, for which we still miss a robust theory. The energy released by these processes has to dissipate for gas to cool, condense, and form stars. How gas cools is thus a key to understand galaxy formation and why it such an inefficient process. Spitzer and Herschel infrared spectroscopy has revealed a population of nearby galaxies with weak star formation and unusually bright emission lines (e.g. [CII], molecular hydrogen), with very broad linewidths. The line luminosities are greatly in excess of that expected by photoelectric heating of the gas, suggesting that they are powered by the dissipation of turbulent kinetic energy. This discovery of large masses of gas not associated with star formation reveal the potentially important, but largely unexplored, role that turbulence plays in the energetics and formation of multiphase gas on galactic scales. In this seminar, I will discuss a few examples where turbulence driven by gas accretion, feedback, and galaxy interactions, which is largely ignored in models of galaxy formation, and captured in current simulations only over a limited range of scales, may have a major impact on galaxy and halos properties.
Would you like to join this Zoom seminar? Please email Donna Hayes.
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