event
Wednesday 29 Sep 2010: Structure of the interstellar atomic phase : the first steps toward star formation
Dr Marc-Antoine Miville-Deschenes - Canadian Institute for Theoretical Astrophysics, Canada
Physics, 4th Floor interaction area 11:00-12:00
It is still unclear what sets the Initial Mass Function of stars but it is likely is that it takes its roots in the turbulent density structure of molecular clouds. If so, understanding the complex HI dynamics that depends on thermal instability and magnetic turbulence, from which molecular clouds form, might provide strong insights on the star formation process itself. In this context I will show how 21 cm and dust emission observations of diffuse interstellar clouds close to the Sun combined with dedicated numerical simulations allows us to put some constrains on the density structure if the diffuse ISM and its link to the properties of interstellar turbulence. In particular I will present new Herschel-SPIRE observations of the Polaris Flare, a young molecular cloud at high Galactic latitude where star formation has not started yet. These observations provide a uniform view of the density structure of the ISM in early stages of star formation at scales from 0.01 to 8 pc. I will present results of a statistical analysis of these SPIRE data (power spectrum and PDF) and briefly discuss the performances of SPIRE at mapping diffuse emission. I will also discuss the first results of 21 cm observations of high Galactic latitude fields obtained with the Green Bank Telescope (GBT) and the Dominion Radio Astrophysical Observatory (DRAO). Originally dedicated to the characterization of Galactic foreground emission for the Planck mission, these observations provides us with a great way to study the properties of the atomic phase, especially the formation of cold and dense structure in the warm HI through the thermal instability.
