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EDITH FALGARONE Reservoir of energy : gravity and nuclear processes. Interact at the scale of SF and starburst Explain the low-rate of SF observed (low compared to what is observed in numerical simulations) Feedback is invoked to explain why the many very low-mass and very massive galaxies formed in simulations are not observed. What is it ? Peak of SF around z=2 Many knobs to turn in simulations (positive and neative feedbacks at stellar and AGN ends) to meet the observations… Interaction of cold streams accreting onto pro-galactic disk shoudl be soruce of turbulence and shocks. Maby too tenuous gas for observations ? Absorption spectroscopy of CH+ line in M82 against continuum of local ULIRGs Strongly lensed submm high-z galaxies can be used to serve as lighthouses to probe the turbulent gas in absorption spectroscopy. CH+ formation endothermic, very easily destroyed, so lifetime is 1 year / fH2 / n50 : it shines where it forms ISM is turbulent : very large Reynolds numbers Energy injection at large scales, destabilisation over a dynamical timescale L/v, cascade in k space to dissipation when advection and diffusion become similar in magnitude. Dissipation scale propto n^(-3/4) while mean free path is propto 1/n and the two are about the same for the diffuse ISM (100 cm-3) Bulk of the motion is in solenoidal modes, not compressive. More compressive in SF regions. Observations of Pety et al. and also simulations by PL. Simulations of PL : half of dissipation is concentrated in 10% of the volume. Sign of intermittency. Expriments of Douady 1991 : filamentary structures of dissipation, living for a turnover time scale of the large scales (rotating disks at top and bottom of the cylinder) so very long if compared to what is expected at their size. Observations of CH+ absorption in high-z lensed starburst galaxies, but also very broad emission lines. Much broader than the CO line emission in the same objects. Description of tasks : CH+ at high-z, turbulence in the local ISM, turbulent magnetic field using the Planck data, the LOFAR conection (how thermal electrons and dust are entwined) Starburst galaxies lie above the main sequence of galaxies SFR vs stellar mass. About one order of magnitude above the MS. 14 observations, 3 have no CH+ line. Those three are known to host AGNs.