Molecular Physics seminar

Diffuse interstellar gas - new results from the PRISMAS Herschel Key Programme

by Dr Carina Persson (Chalmers University of Technology)

FA31 ()


The study of diffuse and translucent interstellar clouds has taken a major leap forward with the launch of the Herschel Space Observatory. The environment in these clouds is very harsh and existing species are therefore small molecules, mostly light hydrides. Most species are, however, very difficult to observe since they have their ground state transitions at wavelengths which normally are not accessible using ground-based facilities. With Herschel, new opportunities have opened for spectrally resolved observations of key species with high sensitivity. The very successful PRISMAS (PRobing InterStellar Molecules with Absorption line Studies) Herschel Guaranteed Time Key Project is a comprehensive spectroscopic study of key molecular line carriers, probing previously unaccessible interstellar hydrides and carbon chains in diffuse and translucent interstellar clouds. The PRISMAS observations use eight compact far-infrared submm-wave sources in star-forming regions as background continuum for absorption measurements of ground-state transitions in the diffuse line-of-sight clouds. By sampling different regions through several galactic arms along very long sight-lines (10 kpc) across the Galaxy, PRISMAS has already begun to have a profound impact on our understanding of the diffuse and translucent molecular gas in the Galaxy.