✎ ohp_meeting_september_2018 [mist]

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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.