Speaker
Prof.
Edith Falgarone
(LERMA/LRA Ecole Normale Supérieure)
Description
The diffuse interstellar medium has long been known to harbor a remarkable molecular richness, that cannot be understood in the framework of state-of-the-art UV-driven chemistry. Absorption spectroscopy performed with Herschel/HIFI reveals unexpected large abundances of small hydrides that are the building blocks of interstellar chemistry in the diffuse medium. Because they are so abundant and need only small amounts of H2 to form, these hydrides are new sensitive tracers, in the entire Galaxy of a poorly known component, the diffuse molecular gas.
Among them, CH+ and SH+ have highly endoenergic formation routes and have been proposed to be specific markers of turbulent dissipation occurring in diffuse molecular gas. Their elusive origin is therefore much more than a chemical riddle: it is rooted in the physics of the diffuse ISM, its turbulent dissipation rate in low-velocity shocks and/or shears, the formation of molecular clouds and connects with the broader issues of star formation and galaxy evolution.
Focus will be on (i) the unique informations on turbulent dissipation inferred from these hydrides absorption spectra in the framework of new chemical models, (ii) the turbulent origin of other species such as CO and (iii) the link between turbulent dissipation and H2 pure rotational emission of the diffuse ISM. If possible, results based on the all-sky CO emission obtained with Planck survey will be shown.